Lossless Audio

Pros

• Compresses files better than any other current lossless encoder
• Available for Windows (win32) and Linux/x86 (binaries only).
• xmms + WinAMP plugin available

Cons

• Very slow encode and decode (realtime on 700-800mhz CPU)
• No source code or format specification available.

It's worth mentioning that the LA foobar2000 plugin doesn't produce bit-identical streams, and the author has shown no interest in fixing this issue

Addtional Reading

• Lossless Audio website
• Lossless Codec Comparison by Rjamorim