Zfone is a VoIP encryption package developed by Phil Zimmermann, the author of PGP. There’s a software utility for Linux, Mac and Windows that automatically detects VoIP calls, negotiates a secure connection, and then filters all call traffic. So now you can have a secure iChat A/V call and protect against packet snoopers and man-in-the-middle attacks!
There’s also a library and source available for the ZRTP protocol so that people can audit the code and embed the technology in VoIP hardware devices. Currently Zimmermann hasn’t released things under a free software license, but once it comes out of beta he’s planning of dual licensing everything, similar to MySQLs GPL/commercial licensing scheme. Who wants to bet that there will be an open-source, open-hardware device platform for this before there’s a commercial product on the shelves? Too cool.