LZMA

LZMA (Lempel–Ziv–Markov chain algorithm) is a general-purpose data compression algorithm and compressed data format. It's described as being an advanced form of LZ77.

Specifications
No written specification seems to exist, only source code. The Wikipedia article has some details about it (probably in violation of their rules about original research, so it might get removed).

Software

 * LZMA SDK

Related formats

 * LZMA_Alone, Lzip, 7z: Compressed file formats that use LZMA
 * LZMA2: An improved version of the data format. See also XZ.

Links

 * Wikipedia article