Here's a list of some nifty cryptography/networking tools Kiel's pointed out lately:

• socat - multipurpose relay; think netcat gone wild -- we used this recently to tunnel UDP DNS queries over ssh
• cryptcat - netcat with twofish encryption (the Debian package adds a man page)
• rsyncrypto - partial transfer-friendly encryption (modified CBC for smaller change windows similar to gzip; less secure than regular CBC)

And a pretty unrelated but useful Red Hat Magazine article on the new yum-security plugin.