Due to patent issues with the Fraunhofer Institute (the people who created mp3) It is illegal to distribute mp3 encoders in binary form aka rpm. I suggest that you use ogg-vorbis, a free lossless audio codec much like mp3:
If you still want to use mp3 then here is a solution:
1.) Install a ripping frontend Grip is probably already installed if you use any mainstream linux distro but I'm kinda partial to RipperX: http://ripperx.sourceforge.net
2.) Install a mp3 codec
this one is better than lame YMMV
Fraunhofer codec (Windows Only) http://www.softnews.ro/public/cat/11...1-1-2-10.shtml
3.) Rip your cds directly to mp3 using grip
If you have preexisting wavs you want to convert try out autolame. I'm sure you could find better software but this is what a quick google search turned up.
If you want to try to find rpms of files use www.rpmseek.com
it is great.