Thumbtacts allows you to search your contacts using one hand.

To find a contact, touch an option (a letter or character string) to proceed to the next set of available matches. Don't see your match? Touch the "More" button. To view additional matching results. You can review your selection so far in the top field. If you make a mistake, simply touch the "Back" button to go back a step, or the "Home" button to start over.