All tech upgrades:

At the password screen type AYZB!RCL, then WRKFORIT

Sound Test:

At the password screen type COMPOSER and the sound test option will be unlocked at the special features screen.

Art Gallery:

At the password screen type EXHIBIT! and the art gallery will be unlocked at the special feature menu.

Infinite Lives:

At the password screen type JPVI?IJC, then RSBFNRL and infinite lives will be opened.

View the Credits:

At the password screen type THATSME!

Making of the Movie:

At the password screen type ?INSIDER

Ace Mode:

At the password screen type U!?!VWZC, then GIVEITUP.

Unlock All Original 10 Missions:

At the password screen type !??QWTTJ, then CLASSIC

Unlock Bonus Mission - Death Star Escape:

At the password screen type PYST?OOO, then DUCKSHOT. The mission will appear above Death Star Attack.

Unlock Bonus Mission - Triumph of the Empire:

At the password screen type AZTBOHII, then OUTCAST!

Unlock Bonus Mission - Asteroid Field:

At the password screen type TVLYBBXL, then NOWAR!!!

Unlock Bonus Mission - Revenge On Yavin:

At the password screen type OGGRWPDG, then EEKEEK!

Unlock Bonus Mission - Endurance:

At the password screen type ?WCYBRTC, then ??MBC???

Unlock Naboo Starfighter:

At the password screen type CDYXF!?Q, then ASEPONE!

Unlock Imperial Shuttle:

At the password screen type AJHH!?JY, then BUSTOUR
Note: ONLY works on Triumph Of The Empire & Revenge On Yavin missions

Unlock Millenium Falcon:

At the password screen type MVPQIU?A, then OH!BUDDY.

Unlock TIE Fighter:

At the password screen type ZT?!RGBA, then DISPSBLE

Unlock Slave 1:

At the password screen type PZ?APBSY, then IRONSHIP

Unlock TIE Advanced X1:

At the password screen type NYM!UUOK, then BLKHLMT!

Unlock Secret BUICK:

At the password screen type !ZUVIEL!, then !BENZIN!

Black and White Mode:

At the password screen type LIONHEAD as a password to play in black and white.

Director's Commentary:

Win a total of 10 medals of any type in the main missions. Or you type the password BLAHBLAH, then go to special features.

Ace Mode:

To get Ace Mode, win gold medals in all 15 missions and complete all objectives on Tatooine.

Bonus Ships:

-TIE Fighter- Steal the TIE Fighter in Imperial Academy Heist and beat the mission.
-Millenium Falcon- Win bronze in ten Slave I-Earn silver medals in ten missions
-Darth Vader's TIE Advanced X1- Win gold in all 15 missions of the game.
- Naboo Starfighter-: Beat the Tatooine Training mission (all objectives, all normal and bonus items) in the morning, afternoon, evening, and night versions.
- Unlock Slave 1 you must earn Silver medals on all 10 normal missions as well as the first two secret missions, Death Star Escape and the Asteroid Field. It will then be available in the hanger.

Documentary:

Beat all ten main missions.

Easier Balloons:

It's more of a hint than a cheat. On the mission, Raid on Bespin. An easier way to destroy the balloons with the turbo lasers on them is to knock out the canister/canisters near the fire is inside the balloon. You get full credit for the kills (easy way for gold).

 

Artillery Guide

Advanced Shields -

This upgrade will change your normally green shield rating to blue allowing you to take a significant amount of additional damage before dying.
Location: On Death Star Attack when you have to destroy the TIEs (the second part of the mission) the upgrade is directly in front of your starting position. As you fly forward, you will see 5 large light gray panels in the shape of a W on its side on your radar. Keep flying and immediately after the W, you will see two dark gray panels that form a rectangle with one red dot on it. This red dot is a laser turret and the upgrade is simply sitting on the ground to the left of it.

Advanced Proton Torpedoes -

This simply upgrades the damage of your proton torpedoes (X-Wing, B-Wing).
Location: On Ison Corridor Ambush the upgrade is inside a piece of a ship that is directly in front of the starting point. Simply fly forward and angle down slightly. When you reach the large hunk of junk you should see the white upgrade inside. Fly in and get it.

Advanced Lasers -

The lasers for all of your ships will be more powerful. More powerful lasers are good.
Location: On the Battle of Hoth after the AT-AT's destroy the shield generator you will be directed to guard your transports by shooting down some TIE Bombers. However, before you do this, go back to where the shield generator used to be and you'll find the upgrade.

Advanced Cluster Missiles -

Your cluster missiles (a secret ship uses these) will hurt more.
Location: On Prisons of the Maw you have to destroy one of the white/silver dome shaped buildings which is sitting next to a lone satellite dish. You can find it on the way to the seven satellite dishes you have to destroy (after you destroy the second group of guns). Now, you may not see the upgrade after you blow up the building, but its' there. Swoop down and skim the wreckage of the building to pick it up.

Advanced Proton Bombs -

Your Y-Wing's bombs will be more devastating than usual.
Location: On Razor Rendezvous you have to destroy a shuttle that tries to fly into the bottom hanger of the Star Destroyer. You'll have to fly directly towards the bottom of the Star Destroyer (ignoring the Redemption's pleas for help). Use your targeting computer to spot the shuttle. It won't be that hard since it's bigger than a TIE and has three wings. Now blow it up and pick up the upgrade that it leaves behind.

Homing Proton Torpedoes -

Your X-Wing and B-Wing's missiles will have homing capability. Press B once to activate, then lock onto a target by holding the cursor near it for a few seconds. You'll see a red colored reticule when the lock is successful. Hit B again to fire. To fire a non-homing shot, simply double tap B.
Location: On Vengeance on Kothlis the upgrade is in a hole in the crashed Star Destroyer's bridge. If you're coming from the nose of the Star Destroyer, the hole is in the left side of the bridge structure. From the back, the hole is on the right side of course. We recommend flying in from the front since it'll be easier to fly out the other side then.

Advanced Concussion Missiles (day) and Spread Proton Bombs (night) -

The concussion missiles upgrade simply give the Millennium Falcon and the A-Wing more powerful missiles. Spread proton bombs are significantly more devastating. Whenever your bombs hit the ground now, eight more bombs will be launched upwards a short distance into the air and forward at a rate of speed that is determined by how fast you were moving when you dropped the bomb. This can really help clean up ground forces on Kothlis, or help you get a gold medal on Prisons of the Maw.
Location: To find these, go to the Imperial Academy Heist level. One can be obtained at night and the other at day. Both of them are in a similar place. As you fly towards the Imperial Academy, you should notice that there are four branches or arms to the base. If you consider the branch with the Shuttle to be the north, then you enter from the south and the upgrade is in the eastern branch during day time, and the western branch during night time. Simply look for the hanger building with the hole in it and either fly through the building or blow it up and skim the wreckage.

Homing Concussion Missiles -

The Millennium Falcon's and A-Wing's missiles will have homing capabilities now.
Location: To get this one, play the Raid on Bespin mission. Quickly take out the balloon and TIE Fighters around the first platform and head towards the second platform. You should see a long ship with three thrusters on the back (there were seven of them in the space portion of the Maw level). If you blow this thing up while it's near the platform, a bunch of the tanks will explode and cause the upgrade to appear. However, if it has moved away from the platform and doesn't cause the tanks to explode, you can still get it. You'll just have to blow the tanks up with your lasers. However, if you don't destroy this imperial ship, the upgrade will not appear whether you destroy the tanks or not.

Homing Cluster Missiles -

Provides homing capabilities for the aforementioned cluster missiles.
Location: In the Battle of Endor when you have to go up against the 2 Star Destroyers, the upgrade will be hanging in space below the left Star Destroyer. The easiest way to find it is by destroying the Star Destroyer then flying around it's docking bay when it's hanging down towards the planet. You probably won't even see it. Just get as close to the docking bay as you can and you should pick it up (note: there is a much smaller docking bay in front of the larger one. Try this one too).

Advanced Targeting Computer -

This provides special functionality for your targeting computer. First off all, you don't have to hold the button down to use it now. This is because you're going to need to use the c-stick to select targets for your wingmen to attack. Once you've located a target with the c-stick, press the d-pad to send your wingmen after it.
Location: To get this nice upgrade, simply play the Strike at the Core mission as usual. However, as you approach the end of the tunnel so that you can see the core in the distance, you'll notice a series of pipes bracketing the lower right section of the tunnel. The upgrade is under the last set of pipes.

Get R2D2 or C3PO as a Bonus Team!:

On Tatooine Training, you can get one of the droids as a bonus item. In the afternoon, get the proton bombs and bomb Jabba's Palace. Find C3PO in the wreck. To get R2D2, destroy the sandcrawler near the Krayt Dragon bones at night.When you find them, each one will respond.