VLC is a popular media player that supports countless audio and video codecs and multiple file formats. Because of such versatility, a lot of folks use VLC as their computer's main video player. And now thanks to ZodTTD, it's available for the iPhone (jailbroken ones only, sorry)!
The project is currently in private beta but a public release is planned for 'very soon'. In its current iteration, VLC supports drag and drop files for MPEG/MPG, AVI, and MP3 formats. Support for FLAC and OGG are well on their way and they are currently researching playback for DivX, VCD, WMA, and WMV. The project is even asking for YOUR input on what codecs you want to see supported, feel free to click the Read link to let your voice be heard.