Whether the iPhone has disabled 3G inside it or not, what's true right now is that for mobile use you're generally stuck with EDGE.  I can't imagine there's any iPhone owner who wouldn't take advantage of a free WiFi hotspot if they could, and now there's apparently a really simple way to find what's available within range.

JiWire [via ModMyiPhone] is a straightforward WiFi finder, which seems to be a directory of known locations rather than a replacement to the iPhone's own active connection search.  That means it'll only have authorised connections listed, which will be fewer than your typical unsecured home network, but you won't run into the bandwidth theft issues you might have if you go around hooking up to people's broadband willy-nilly.

The strength and value of any such directory is the quality and ongoing upkeep of its data.  Well-known areas such as major cities tend to be better mapped than smaller, more out-of-the-way locations.  The JiWire site doesn't seem to be working for me at the moment, so I can't tell where they get their information from or if there's a way to update it with your own free-network discoveries. 

What I'm wondering is when shared-WiFi company FON will start promoting their setup as the ideal way to secure free iPhone WiFi access when on the road.  Yes, it wouldn't really require much tweaking on their end (beyond an iPhone-Safari friendly page layout, perhaps) but I can see it being a good publicity drive.