Just wanted to drop a heads up that the iPhone Web Development mailing list on Google Groups is lively, helpful and full of great people. If you’re interested in developing web sites specifically for the iPhone (whether you do so to expand an existing site or creating a site specific to iPhone use), you’ll probably want to check out this group.
A nice place to show off and discover iPhone apps is gridgets.com. These guys also have some background on iPhone icon sizes and a Photoshop template: gridgets.com/backpages/.