Move between users?

In the Accounts system preference pane, go to "login options" in the lower left. Make sure "Fast user switching" is enabled. Then in the right part of the menu bar, click on your user and drag down to the one you want to log into.

Go to -> System Preferences -> Accounts -> Login Options and click "Enable fast user switching." After doing this you will notice your user name in the upper right hand corner of the desktop's drop down menu. Click on your user name and a menu will drop down allowing you to switch to any other account on your machine with out logging out of your own account. When you want to return to your own account use the same procedure.