If you are dealing with thousands of user name and password then you should surely check out KeePass.
KeepPass can stores and manages your user name and passwords in a single secure file in your machine encrypted using one master password. You now just need to memorize single password instead of thousands.
It can even suggest you strong random password based on provided number of characters and other consideration like options to include special characters, having combination of lower and upper characters in password etc.
When you want to use web site password, just double click (or press Ctrl+C or right click on any field and click "Copy Password To Clipboard") on list item to copy password into the windows clipboard. No need to reveal your password on the monitor to use it. And when you paste your copied password on login form, it will automatically remove copied password from your clipboard.
Further, it you didn't paste your copied password within specified time then KeePass will also automatically remove copied password from the clipboard.