(Warning: Stale branches can cause issues - See wiki for help)
Remember to make the "logged in" state clear enough to help the user know the current state.
Figure: Bad example on Web form - The user is logged in, but it isn't very clear
Figure: Good example on Web form - It's clear that the user is logged in
Figure: Good example - TimePro use avatar to state user logged in
Figure: Good example - SugarLearning use avatar to state user logged in