If you are used to call 411 to get information then this is good news: Jingle Networks launched a free (advertisement based) 411 service. The service works basically like regular directory assistance. You dial the number; say the location and listing name. The only difference is that you must listen to a short advertisement from a related service.
You can find more information on their site at http://www.free411.com/ or by simple trying the service calling 1-800-FREE411 (1-800-373-3411). Being a 1-800 number you can invoke the service for free using a telephone line or GizmoProject/ SIPphone network.
After some research in this direction I discovered other 2 services that claim to offer free 411 assistance. Feel free to test them and drop me a comment with your findings.