LAME

Lame is perhaps one of the most popular of audio codecs. It is used with MP3 container and is what the majority of software applications use for ripping CDs. It uses a lossy algorithm to compress audio, mainly for streaming purposes and portable music players.

As far as its comparison with Ogg Vorbis, WMA and AAC goes it seriously is lacking. However, because of the popularity of the MP3 format, and the wide acceptance with majority of audio players people gladly overlook the compromise on quality and file sizes.

But due to the push from Microsoft for its own Windows Media Format (WMA/WMV), has resulted in a lot of devices being both WMA and MP3 compatible. WMA though is free from patent woes still isn’t open source like LAME.
Also Check MP3Dev