Deep sleep keyboard shortcut
The two keyboard shortcuts for sleep:
Display sleep: Shift+Control+Eject
Computer sleep: Command+Option+Eject

Source: http://support.apple.com/kb/ht1343

To change the default sleep mode to hibernate (in the terminal):

sudo pmset -a hibernatemode 25


I don't think there's any way to preserve the normal sleep behaviour and have a separate keyboard shortcut for hibernation without writing a script that changes to hibernate mode when called and changes it back after, somehow, but this command does work on my MBP. There's a number of options for sleep that you can see with:

man pmset