According to Apple's Tech Specs for the newest iPods (the iPod Touch specifically) these are the formats that will play on current generation iPods.
Audio
- Frequency response: 20Hz to 20,000Hz
- Audio
formats supported: AAC (16 to 320 Kbps), Protected AAC (from iTunes
Store), MP3 (16 to 320 Kbps), MP3 VBR, Audible (formats 2, 3, and 4),
Apple Lossless, AIFF, and WAV
Video
- H.264
video, up to 1.5 Mbps, 640 by 480 pixels, 30 frames per second,
Low-Complexity version of the H.264 Baseline Profile with AAC-LC audio
up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file
formats; H.264 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per
second, Baseline Profile up to Level 3.0 with AAC-LC audio up to 160
Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; MPEG-4
video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple
Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v,
.mp4, and .mov file formats