Google has launched a free 411-style information service. It's not the first free one, by any means, but since it's Google's, I'll have higher expectations about its usability. There's another one available -- that's even older than Google's service. It's too bad you have to pay for e911 service, because doing the same won't send your name and address to your local PSAP.
The catch is, when you're dialing for information, you're at the phone, not the computer, and you may not have memorized the number. (1-800-GOOG-411.) If you're running Asterisk, you can easily reprogram 411 to go to the free 411 service of your choice. Just add the following lines to your extensions_custom.conf in /etc/asterisk:
[from-internal-custom]
exten => 411,1,Answer
exten => 411,2,Dial(SIP/mytrunkname/18004664411|300|)
exten => 411,4,Hangup
Update: FreePBX has an excellent tutorial on setting up free 411 service with Asterisk.
Google's not the only free 411 service, and the others mentioned can also do residential listings.