Archiving/Zipping Software What compression application would allow you to also encrypt a file?
The only free (albeit not open source) Mac OS GUI compression utility I'm aware of is B1. It does support password protecting archives, although not encrypting them.

Two commercial applications that do support encrypted archives are:


Winzip
StuffIt


That said, if you're happy using the command line, the zip utility provided with Mac OS can do password-based encryption (look at the -P option).