Monkey's Audio

Features:
Efficient (fast and great compression) – Monkey's Audio is highly optimized and highly efficient
Perfect sound – absolutely no quality loss, meaning it sounds perfect and decompresses perfect (it's lossless!)
Media Center™, Winamp™, and more support – supported by many popular players and rippers
Easy – the Windows environment interface is both powerful and easy to use
Free – Monkey’s Audio is completely free!
Error detection – Monkey’s Audio incorporates redundant CRC’s to ensure proper decompression of data (errors never go unnoticed)
Tagging support – Monkey’s Audio uses its own extremely flexible APE Tags so you can easily manage and catalogue your Monkey’s Audio collection.
External coder support - you can use Monkey's Audio as a front-end for all of your encoding needs
Freely available source code, simple SDK and non-restrictive licensing - other developers can easily use Monkey's Audio in their own programs -- and there are no evil restrictive licensing agreements
Description:
Monkey’s Audio is a fast and easy way to compress digital music. Unlike traditional methods such as mp3, ogg, or lqt that permanently discard quality to save space, Monkey’s Audio only makes perfect, bit-for-bit copies of your music. That means it always sounds perfect – exactly the same as the original. Even though the sound is perfect, it still saves a lot of space. (think of it as a beefed-up Winzip™ for your music) The other great thing is that you can always decompress your Monkey's Audio files back to the exact, original files. That way, you'll never have to recopy your CD collection to switch formats, and you'll always be able to recreate the original music CD if something ever happens to yours.