And atool (http://freshmeat.net/projects/atool/) also does roughly the same thing. Perhaps the projects should be merged eventually.
Another Perl script that does more or less the same thing is ZZIP (/projects/zzip). (Not to be confused with zzip (http://www.zzip.f2s.com/) the block-sorting compressor.)
An open, cross-platform journaling program.
A scientific plotting package.