Mac OS X Leopard only: If you tried installing our favourite password manager for Mac, KeePassX, on Leopard, you already know it doesn't work. (When you launch it, it crashes, without ever opening.) Apparently someone who knows more about KeePassX than we do figured out it's a problem with the Qt development package installed with it. Here's how to get KeePassX working on Leopard. Download and install the open source edition of Qt.
Once that's done, in the Terminal, run this command:
rm -rf /Applications/KeePassX.app/Contents/Frameworks
When you launch KeePassX, all will work as you expected. You run into any other Leopard incompatibilities? Tell us about it in the comments.