I like LastPass, personally; the browser integration's pretty damn good.
Anyways, how it works is you sign up and put in a password, and this master password is used to lock everything up, so pick a good one and don't forget it. Then you save passwords to it, and it's encrypted
before they send anything to the server. It also helps you generate passwords and stuff.
Then when you go to a login form, it'll give you an option to fill it in automatically. Also, if you have multiple logins (e.g. throwaway email addresses) it'll give you a choice of which to login with.
You can login to LastPass from any computer, so long as you've got the master password. You can also get a copy of Firefox Portable and install it into that.
Another one you may want to look into, if you don't like LastPass, is
KeePass, which is open-source. Don't think the browser integration's as good though. There's a portbale version available on PortableApps so you can stick it on a USB drive and take it with you.
These two were also in my bookmarks. I haven't had a chance to test them, so
use at own risk:
http://www.roadkil.net/program.php/P21/Password Store
http://www.cherbox.net/
Password managers are helpful because you can use many different passwords without getting them mixed up in your head or forgetting them. I started using LastPass after my accident, because my memory is shot and I have trouble remembering things.