I use this program for a lot of sites. If you have different usernames/passwords for all different sites, this program would be good for you.
It is an add in for IE/Firefox. Basically, you set up a very difficult Master password. then you go to a site, login, and it asks you if you want it to record it. If you say yes, it will. Then all you have to do is click yes. Then the next time you want to go to that site, all you have to do is click the login drop down box (you can be on any site when you do this) and it will automatically go to that site and log you in (after you enter in the master password).
Another feature is that it will fill in forms for you automatically. You can store any amount of info, and then it will fill it in for you when you click on a button with your name on it.
http://www.roboform.com/