If you are forgetful, constantly curious, or gifted with a craptastic sense of direction, you should definitely check out Google SMS. The service is simple-- send an SMS from your phone to 46645 (that's GOOGL on the keypad.) For instance:
1. Yellow pages: "Radio Shack 10007", "Gray's Papaya 10013"
2. White pages: "Michael Bloomberg, New York, NY"
3. Directions: "JFK to 345 Chambers Street, NY NY"
4. Movies: "Rent 10013", "movie: theaters 10065"
5. Weather: "w 10012" or "weather 10012"
6. Prices: "xbox360" or "price xbox360"
There's a ton of other search queries you can do-- stocks, calculator, general search-- to see them all check out this tip sheet or print the wallet card PDF out for frequent reference. When in doubt, just send 46645 whatever you can think of-- Google is suprisingly good at figuring this stuff out.
Related: If you use Dodgeball, you can do location lookups just by texting "? nameofplace" to email@example.com, and if you have a Java-enabled phone, you should check out the Mapquest maps app, which can display all sorts of GPS location info.
Do you have any other SMS services or cell phone downloads you'd recommend?