USING YOUR MAC IN THE SUN?
Then use this ‘magic’ key combination to change the whole interface into a high contrast black and white version. Press these keys together (note the dash is only there to make this combination more readable):
CTRL-ALT-COMMAND -8
Very useful if you happen to sit in a train and need to do some work while the sun is shining.
If you want to change it back just use the same combination. I wonder if Ubuntu has something similar?
— ♦ —

Ubuntu does come with a high-contrast theme as well as one with enlarged type. However, there is no fancy key-combo to put into place. You simply have to change your theme in the preferences, which is simple enough. Let me know if you’d like a screen shot.
@Simanek,
Thanks for the tip! I hadn’t noticed that Ubuntu has a high-contrast theme. Would be great though if you could switch to it using some fancy key combo