There are a number of different media file types. Here are the basic ones and the applications used to play/convert them.
- MPEG - .mpg, .mpeg - QuickTime Player will usually play these files. Some files may require VLC or Mplayer.
- MPEG2 - .vob, .mp2, .mv2 - QuickTime Player w/ the MPEG2 Playback add-on, or VLC for free.
- MP3 - .mp3 - QuickTime Player, iTunes, VLC, etc. Just about anything will play MP3s now. My personal favorite is iTunes 4.
- AAC/MP4 Audio - .aac, .mp4, .m4p - iTunes will play most of these audio files, QuickTime Player will also play these AAC/MP4 files.
- MPEG-4 Video - QuickTime Player 6 and up will play MPEG-4 video files.
- OGG - .ogg - VLC is your best bet. Mplayer may also work.
- Windows Media - .wma, .wmv, .avi, etc. - For non-MS apps, VLC should handle most WM files. There are a few that don't work though. In that case, you will need Flip4Mac.
- FLAC - .flac - This app will decode the .flacs into MP3s or AIFFs. MacAmp X Lite and the FLAC plug-in will allow you to play the files the way they are.
- Shorten - .shn - Shorten X will convert the .shns into .WAV files which can then be converted into MP3s or AACs using iTunes. MacAmp X Lite and the Shorten plug-in will allow you to play the files the way they are.