Everyone loves free internet these days. Airports offer it, coffee shops offer it, even some entire parks or cities offer it. If you have wireless internet of your own, why not use it as a lure for those garage salers with wireless devices? Opening up your secure network, however, can be dangerous for your files and computer, so it's best do know the risks ahead of time and take precautions.
Blogger Bruce Schneier recently wrote about the reasons he runs an open wireless network. In his post, he also covered all of the risks of doing so (and rebutted them). The biggest reason many people do not run open wireless networks in general is the risks of illegal activity occurring on their network, which, if it led to legal action, would include them in the time-consuming, expensive process, not the user who just plugged in for free. It's also dangerous because without the proper precautions, people can access your computer and files. Internet Service Providers, or ISPs, may be irritated if you're constantly running an open network and sharing your bandwidth with customers who haven't paid -- but for just one weekend, it's not really a big deal.
Okay, so you've decided it's a go on the open network. You should probably make up a sign to put on your lawn or house mentioning the network, to draw people in. Then you need to remove the password from your network, which can be done in the Network Connections (or similar control area) of your computer. You may have to walk through some of the installation or configuration steps again, but it shouldn't take much to get rid of that security option.
And you're done! Now, you're probably thinking, how am I going to keep myself safe with an open network? The easiest and most obvious answer is to use a free internet filtering program, like K9 Web Protection, and block some specific sites you don't want your customers to be accessing (perhaps torrent and other file-sharing sites, pornography sites, and other illegal or offensive content you could be held liable for). K9 Web Protection allows you to block entire categories, making it easy for you to eliminate threats in one fell swoop. You should also make your computer invisible on the network, preventing customers from accessing your files.
If you're leery of opening the network entirely, you can always set a new, simple password and require users to sign a release form, saying they will not conduct illegal activity, sue you for harm to their devices, or squirm out of the blame if something does go wrong and it's their fault. People may grumble about this, but the chance to snag some free bandwidth may be worth a signature. Once they've signed, you can give them the password and they can browse to their heart's content. Just don't forget to change the password back once you close up shop!
You may find that customers hover too long, standing around to use your wireless network. If that's the case, you can either politely ask them to leave, or use it as a sales opportunity: approach them with a question of "can I help you find anything?" or "is there anything you're interested in?" once in a while. If it gets to be too much, you can just shut off your router and let them discover that their connectivity no longer works.
Speaking of internet resources, have you checked out GarageSaleCow.com lately? With tons of listings across the country and a plethora of free resources, it's the nation's largest garage sale Web site!