You may or may not know that Twitter was "hacked" recently and the key lesson from that was that passwords are essential - good passwords that is. Changing them every so often is also something you should do. It's a pita but it has to be worth it.
PC:
http://www.pctools.com/guides/password/ free
Everything:
http://keepass.info/download.html free
http://fpx.de/fp/Software/Gorilla/ free
Mac:
http://agilewebsolutions.com/products/b/1Password $40
There will be others that cost or are free.
There are ways to sync these using Dropbox - http://getdropbox.com - across machines.
The blog I need help with is mark.wordpress.com.