If you are like most modern Internet users, you subscribe to dozens of services and websites and need an account for each one. Using the same username and password on all of these sites is easy but a terrible idea from a security perspective. Enter KeePass. KeePass is an encrypted software safe for all of your usernames and passwords. It is multi-platform and open source which is important to me. I use it under Linux, Mac OSX, Windows, iPhone/iPad, and Blackberry. To use version 2.0 under Linux, you need to run it under Mono.
One problem I ran into when using KeePass under Linux is that copy/paste does not work out of the box in its default configuration. Google pointed out that Linux has two copy buffers. Details can be found here. This led me to the tool autocutsel and a post on Superuser. After running:
$ autocutsel & $ autocutsel -s PRIMARY &
I can now copy/paste from KeePass.
I recommend using a very long passphrase for your master password. I synchronize my KeePass database in Dropbox so I can access it from all devices anywhere I am as long as I have an Internet connection.