All popular web browsers offer a password manager option to store usernames and passwords of the visited websites. It is possible to recover these usernames & passwords and in some cases view dates and times when a person registered/logged in with these credentials the first time.
1. Internet Explorer - IE PassView
2. Mozilla Firefox - PasswordFox v1.10
3. Safari – Method applicable to several web browsers
4. Opera – Unwand
5. Google Chrome - ChromePass v1.05
There are some other utilities incl. commercial versions, which I have not tested. The above mentioned tools are free and tested to be working.