GX::Transcoder: Batch converter for tons of audio and video formats

GX::Transcoder is a freeware batch converter for audio files that supports an ungodly number of different formats. I won't even list them all, just visit the site. In addition to converting whole swaths of files at once from almost any format to almost any other format (and preserving ID3 et al tags in the process), GX::Transcoder also comes with a handful of plugins which do video conversion (albeit not among as many formats as for audio) and playback, CD ripping, and more. It won't win any beauty contests, but workhorses like this seldom do.