Audacity tutorial: Converting to mp3 or AAC and other formats, example: Matthew Smith - epic orchestral synth music for film and game effects; Buanzo's LAME mp3 library
Download the latest version of Lame MP3 for Audacity free in English on CCM - CCM
Installing and updating on Mac OS X - Audacity Development Manual
Audacityで編集した音源をmp3で書き出す方法 | Oto Gate
Audacity
Download Lame MP3 Encoder for Windows XP (32/64 bit) in English