TransKode is a KDE/Qt based frontend for varios audio transcoding tools.

Supported input formats:
* aac, ape/mac, bonk, flac, la, mp2, mp3, mp4/m4a/m4b, mpc/mpp/mp+,
  ofr, ogg, pac, shn, spx, tta, wav, wv
* other media formats decodable by ffmpeg, mplayer, xine or gstreamer
  (mp1, wma, ra/ram, ac3, dts, mka, asf, avi, mpg/mpeg, wmv, qt/mov,
  rv/rm/rmvb, flv, 3gp, vob...)

Supported output formats:
* aac, ape/mac, bonk, flac, la, mp2, mp3, mp4/m4a/m4b, mpc/mpp/mp+,
  ofr, ogg, pac, shn, spx, tta, wav, wv
* other audio formats encodable by ffmpeg or gstreamer (ac3, wma, asf...)

WWW: http://sourceforge.net/projects/transkode/