I take a look at one of the more interesting security tools to hit Apple desktops in quite a while in TrueCrypt 5.0 Brings Plausible Deniability To OS X Users over on The Apple Blog:
If you need/desire cross-platform compatibility, then TrueCrypt is a perfect choice. You can encrypt a virtual disk image onto a USB drive and take it from Windows to Linux to OS X and gain access to your all your secret data, something that is not possible with OS X secure disk images.
ArpSpyX updated to 1.2 and I've got details over at The Apple Blog.
(Poll via comments: is this technically a 'quick hit' or is it just redundant given the "My posts over @ TAB" in the sidebar?)