Eyes-free dialing.
Slide your finger in the direction of the number you want — always starting at 5, you can then go up and to the left for 1, or down and to the right for 9, and so on.
Press Menu to access your Phonebook. Press the Dial button to call.
Featured in the NY Times:
http://www.nytimes.com/2009/01/04/business/04blind.html