I'm used to hittig Winkey-E to bring up Explorer on Windows. So, I want to have a similar key binding on Ubuntu. Here's how I did it:
Step 1: Disable current key binding of Winkey-E.
System->Preferences->Advanced Desktop Effects Settings
Go to Desktop->Expo->Bindings
Click on Super-E and disable it.
Step2: Add new bindings
Go to /Apps/metacity/global_keybidings
Set run_command_1 to < super >E (without any space)
Go to /Apps/metacity/keybinding_commands
Set command_1 to /usr/bin/nautilus
You're done. Enjoy!