Useful Keyboard Hotkeys for Linux

Alt + F2 ➜ Graphical Run Application
Ctrl + Alt + L ➜ Lock Screen (Works in almost all distros)
Ctrl + Alt + F1 ➜ Switch to the first text terminals.
Ctrl + Alt + F7 ➜ Switch to the first GUI terminal (if X-windows is running on the 7th terminal, where it typcially is).

Source: linux.about.com