Just a collection of utilities. Mostly bash scripts. Currently the tools are:

jpegrescan - modified version of http://akuvian.org/src/jpgcrush.tar.gz
It keeps EXIF data by default and supports arithmetic coding as well

jpegfolder - script that uses jpegrescan on a given folder. keeps all EXIF data.
Great for losslessly slimming down family photos.

gzcrush - script that uses several utilities to create an extremely small gz file.
Even smaller than zopfli I might add. The script has several dependencies:

KZIP: http://advsys.net/ken/utils.htm or http://www.jonof.id.au/kenutils

kzip2gz: http://encode.ru/threads/1630-kzip2gz-a-zip-(single-file-amp-deflate-compression)-to-gz-converter

huffmix: http://encode.ru/threads/1313-Huffmix-a-PNGOUT-r-catalyst

deflopt: http://www.walbeehm.com/download/

defluff: http://encode.ru/threads/1214-defluff-a-deflate-huffman-optimizer

zipcrush - similar to gzcrush except it works on zip files. requires KZIP and ZIPMIX as well as deflopt and 
defluff.