Yes. There a couple of options.
1) You can enable CTRL+SHIFT+BACKSPACE. This three keys will work like CTRL+ALT+SUPR, but they will only restart the GUI.
2) From the command line (press CTRL+ALT+F1 to get to a console) you can restart the Ubuntu display manager (which lets a user login to her preferred GUI) by entering:
sudo service lightdm restart
3) Finally you can restart just unity. It will reset your GUI (all the windows and the bars), but it will not kill any program. After the restart you can continue working where you left it. Enter:
or if you are restarting from the console (after pressing CTRL+ALT+F1), enter:
DISPLAY=:0 unity --replace