Kismac
Here’s a handy hint for finding wifi when you’re away from your regular internet connection: use Kismac, a wireless stumbler for Mac OS X, to find open networks in your vicinity. Not only will Kismac tell you what networks are present, and whether they have WPA or WEP protection or are open, it will also give you an indication of their signal strength. Being able to keep an eye on the signal strength is just what you need when you’re trying to position yourself to pick up a weak wifi signal (as I have been this week).