I thought I wrote about this a while ago, but a quick search didn’t reveal anything, so here it is.
Google offers free 411 service to look up business phone numbers.
The neat thing about it is that Google will connect you directly to the business, so you don’t have to deal with writing down the number like with other free 411 services.
Another neat feature is that Google will send you an SMS with all of the business details including their address!
Both of these access numbers are free from any phone:
Goog 411 Linky