Western Digital WD TV HD Media Player (WDAVN00)
While it isn't infallible, the Western Digital WD TV HD Media Player plays back a wide array of audio, video, and image files on your TV without the need for a computer.
http://reviews.cnet.com/Western_Digital_WD_TV_HD_Media_Player_WDAVN00/4505-6463_7-33396690.html?subj=fdba&part=rss&tag=MR_Video+Players+and+Recorders