1up.com have been kind enough to round up a list of all the media formats PS3 will support:

Blu-Ray (ROM, -R, -RE); DVD (ROM, -R, -RW, +R, +RW); CD (ROM, -R, -RW, Super Audio)
MPEG-1, MPEG-2 (PS, TS), MPEG-4 SP, and MPEG-4 AVC/H.264
ATRAC, AAC, MP3, and WAV
JPEG, GIF, PNG, TIFF, and BMP

Not really many surprises there, but nice to know for completion's sake.