bzip2 - version 1.0.1

From the README and man pages:

bzip2, a block-sorting file compressor. 

bzip2 compresses files using the Burrows-Wheeler block sorting text
compression algorithm, and Huffman coding. Compression is generally 
considerably better than that achieved by more conventional LZ77/LZ78-based
compressors, and approaches the performance of the PPM family of statistical
compressors.