Trying "Asunder", one of the ones from Marvo's link. Wouldn't let me do MP3s to start with so had to install "lame", the MP3 encoding library (frontend) from the Software Centre. Rips CDs fine into the separate MP3s.
Lame is a codec, the program you install for ripping is basically just a front-end to make it usable, the codec is the software that actually does the encoding of the music. It's worth installing the Lame codec on your PC as a separate item because there's many other applications will look for it when they're installed.