The LAME Project
LAME is a high quality MPEG Audio Layer III (MP3) encoder licensed under the LGPL.
It is developed as an educational tool to be used in learning about MP3 encoding. The goal of the LAME project is to use the open source model to improve the psycho acoustics, noise shaping and speed of MP3.
LAME is not for everyone - it is distributed as source code only and requires the ability to use a C compiler. However, many popular ripping and encoding programs include the LAME encoding engine, see: Software which uses LAME.
Using the LAME encoding engine (or other mp3 encoding technology) in your software may require a patent license in some countries.