Members of Banner exchange Networks recieve free advertising in proportion to the number of banner ads displayed on the member site.
Normaly this ratio is 2:1. Meaning each member is allowed one impression for every 2 displays of banners on her site.

Banner exchange programs make their money by displaying paid for advertisments on the same member pages. On a network that operates on a 2:1 ratio half the banners displayed will be paid for advertisments and the other half, reserved for members.

The Link Exchange

Join linkexchange 1 credit per 2 adviews Max banner size - 8k max banner dimensions - 400*40 Animation    Targeting    Sample Banners Used to be called the Internet Link Exchange. And has grown to be the most popular and reputed banner exchange program on the web, With over 100,000 members. Recently they introduced targeted advertising and animated banners. As well as increasing the maximum size of banners from 7k to 8k. LE banners usualy loads faster than Smartclicks or Free4all banners. but my clickthrough ratios (CTR) are lower than with Smartcliks for similar banners LE also provides excellent statistics about ad displays, click throughs and viewings. Which happen to be the only source of web site stats available to some members. LE also provides their members with a lot of resources including free banner creation, free scanning services and tips on site design and promotions. Most these services are provided by volunteer LE members

Smartclicks

Join Smartclicks 1 credit per 2 adviews Max banner size - 10k max banner dimensions - 400*40 Animation    Targeting    Sample Banners Smartclicks was perhaps the first major bannerexchange network to offer targetting and animation. However Smartclicks is not as popular as the Link Exchange. This is probably due to the fact that smartclicks banners take longer to load than LE banners and many visitors whould move away without seeing the banner. As a result the website gets no credits But smartclicks makes up for it in other ways such as an excellent targeting control feature. It will Display your banner on all it's catogories and choose the best catogories for your banner depending on the CTR for each catagory. Of course the catagories can be chosen manualy instead.

Free4All

Join Free4All 1 credit per 1.5 adviews Max banner size - 10k max banner dimensions - 400*50 Animation    Targeting    Sample Banners Free4all banners load much slower than both linkexchange and Smartclicks banner. And their server has a habit of crashing. They offer lots of other sevices like mini search bars, jump bars (navigation tools), and even offer to setup your own banner network. But most these services a require a stop over at the free4all website which most web developers could not swallow. Every free4all banner on this site was pulled on the 7th of Nov as they were not accumilating credits. They offer 50 free credits for each new member that a web site directs their way, so if you were thinking of signing up ......     http://www.free4all-exchange.com/cgi-bin/join.cgi?account=1957 ;-)