US-centric: Our gadget-obsessed brothers at Gizmodo report that many AT&T hotspots—including Starbucks and Barnes and Noble—have started offering free Wi-Fi access to iPhone users. With a little ingenuity, the same free Wi-Fi access can be granted to your laptop. Using it from your iPhone, you just connect to the hotspot and give the site your iPhone number. To get the same access on your laptop, the key is to fool the hotspot into thinking your browser is still an iPhone. Here's how:
To masquerade as an iPhone, you'll need to tweak your browser's user agent, which web sites use to identify your browser when you connect to the site. In Firefox, you can install the previously mentioned User Agent Switcher. In Safari, you can select the iPhone user agent through the Develop menu (which you can enable by navigating to Preferences -> Advanced and checking "Show Develop menu in menu bar." Likewise, Opera has user agent switching built in. On the non-Safari browsers, you'll have to manually add a new iPhone user agent like so.
Now that you're all set up with your spoofed iPhone user agent, head to the hotspot page and enter your iPhone number (or, if you've got permission, maybe the number of an iPhone owner you know).* Once you're done, you should hopefully have free hotspot access from your full screen rather than your tiny iPhone screen.
I haven't actually been able to verify this yet (though there are reports of success), so if you give it a try, let's hear how it worked for you in the comments.
*One Gizmodo reader using his unlocked iPhone with T-Mobile reports that entering his T-Mobile number worked, but your mileage may vary.