ilovefreewifi is a community listing of free wifi hot spots you can pull up with your phone.
It's easy. You send your address or location to ilovefreewifi and it responds with two messages detailing six nearby free wifi spots. If you need additional information you respond with the location code and it'll give you hours of operation, etc.
You can also browse their listing via a Web-enabled phone or before you leave the house! They've got listings for most major cities in the US and it's growing. Thanks to Lia at Gizmodo