From the fans
For Fan art, see Rei's Sei Juyshi Bismark page, or Buddy Rose's Saber Rider page.
The only Fan Fiction (I know of) at this time is Zorina Skye's A Rider on the Force.
The theme song as .WAV file 973kb (recorded by the author of this page)
The ending theme as .WAV file 683kb (from SoundAmerica)
The complete theme as .MP3 file 679kb (from this Saber Rider page, but I couldn't find out who made it.)
MIDIs For Ears, lots of Saber Rider (and other anime) MIDs, guitar tabs, lyrics...