ShrinkIt

ShrinkIt is an archive format for the Apple II series (with also some Mac versions, but not always necessarily compatible cross-platform). It was created originally for the IIgs (relatively late in the history of the Apple II platform), but ported back to some of the other Apple II models. It uses LZW compression.

Links

 * Hacking data compression (gives lots of format details)
 * What are ShrinkIt files?
 * ShinkFit X - Mac OS X archiver compatible with ShrinkIt
 * ShrinkIt documentation