FFmpeg

FFMpeg is an open source library for encoding and decoding different types of media files, generally MPEG and MPEG-based files.

FFMpeg supports lots of codecs: the main ones are included on the codecs page. If you want the full list, (including different spellings for the same codec), the source code lists them all (theres way to many to list them all here ;-). In source:modules/codec/ffmpeg/ffmpeg.c look under Codec fourcc -> ffmpeg_id mapping (that bit changes the codecs you type in to vlc to ffmpeg's internal codec names).