Try this out... 411 via an 800 number with no advertising (for now). Google Labs is experimenting with Google Voice Local Search. Call 800-GOOG-411, give it a city and state, ask for a listing, and it will return the results and connect you to the listing you choose.
The whole thing can be voice-navigated. I called and found my church and was connected to the main number. Way cool.
You can use Per-Call Blocking (aka Selective Blocking) by dialing *67 before dialing the phone number. You'll have to dial *67 every time, though.
While Google promises to respect your choice to block caller ID, you should know that they don't have to. Because the other party pays for the call, FCC rules allow toll-free companies to use Automatic Number Identification (ANI) technology to identify you even when caller ID is blocked. FCC rules, however, limit parties that own toll-free numbers from distributing the numbers identified through ANI.