http://www.twonkyvision.de/
http://tversity.com/
http://xbox360forums.com
From the Twonky website:
Content formats
Music: MP3, WMA, WAV, 3GP, M4A, MP4, LPCM, Ogg Vorbis, FLAC, MP2, AC3, MPA, MP1, AIF, ASF
Photo: JPEG, PNG, TIF, BMP, GIF
Video: MPEG1, MPEG2, MPEG2-TS, MPEG4, AVI, WMV, VOB, DivX, 3GP, VDR, ASF, MPE, DVR-MS, Xvid, M1V, M4V
Internet Radio: vTuner, Shoutcast
Playlists: WPL, PLS, M3U
Note: the actual formats supported depend on the individual client devices. The current version of TwonkyMedia does not provide transcoding functionality.
From the Tversity FAQ section:
What media formats are currently supported?
The current version is designed such that almost anything you can play on Windows Media Player, whether it resides locally on your computer or located on the Internet, should also play on any of the supported devices, despite the fact that these devices do not natively support many of these media formats. You can also play Quicktime video and Real Media videos (including rmvb), however for the time being you cannot stream Quicktime or Real from the Internet. To give a more precise definition, any media format that has a Directshow decoder will work with TVersity as long as you have the directshow decoder installed, this includes:
WMA, WMV, MJPEG, DVR-MS, AVI (including Divx3/4/5/6, Xvid, and others)
MPEG1/2/4 (including H.264), MP3 and AAC
Qucktime MOV
Real Video/Audio/RMVB
OGG Vorbis and OGM
FLAC, WMA lossless, Monkey Audio (APE), Musepack Audio (MPC) and Wavpack
Flash Video
Matroska (MKA and MKV)
Karaoke CDG/BIN (Directshow filters here, the ones from DirectX Karaoke and Troubadour Karaoke are not compatible with TVersity)
And many more…
Please refer to the Download page for some links to third party software.