Razorlame: it is a freeware front end graphical user interface - just google it.
Lame encoder - freeware and widely recognised as the best MP3 encoder. It can be download from rarewares.com iirc.

Unzip the Lame encoder into a directory. Unzip Razorlame into another directory. When you start Razorlame it will automatically look for and detect the Lame encoder - if it doesn't then just point it to the right location.

Now you're ready to go. They are a brilliant combination capable of encoding at all sorts of bit rates in single file mode or batch mode.

More info at www.hydrogenaudio.org

This is the tool I use.

[Edited on 25-5-2006 by twpd]

I use itunes.

edit - preferences - advanced - importing then check your choice of encoder, in this case mp3. Now if you right click a file in the library you can convert to mp3.

Cheers guys - I'll have a go with those...