Being able to connect on the fly is incredibly important. Whether you're taking a work trip, a working vacation, or just want to get out of the office for the day, you're always ready to go if you can set up your laptop and get an internet connection. (Though you'll be happier if you have a few of these other tools as well.)
Sniffing out a wireless network isn't always easy. In airports, for example, Free WiFi network offerings could be scams. There are a few reliable places to get WiFi (like Starbucks and Borders, among others), but doling out for the ludicrously priced TMobile HotSpots can be infuriating. If you've got a FON router at home, there are a few more free options open for you, but their network isn't quite big enough just yet for that to be a reliable fallback.
Instead, check out WeFi, a Google Maps mashup that relies on user input to show which places have free WiFi. While it's also still getting going, it's a great resource for finding local businesses that give their customers free internet access. (You could also use it to snag WiFi from random places, but remember that some judges seem to think that's against the law.)