Quantized Indexing is a new practical form of combinatorial (enumerative) coding. Under proper conditions it can be faster and tighter than arithmetic coding. There is a demonstrative source code, but no off-the-shelf working compressor though. There were quite a lot of talks on QI in comp.compression newsgroup recently. See
this'>http://groups.google.com/group/comp.compression/browse_frm/t... thread as an example.
