This isn't quite Nikola Tesla's "Free electricity for everyone" but I'll take it.

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Wireless net.access is not yet ubiquitous, but it's pretty common and becoming moreso every day for a variety of reasons. Net.access is definitely in enough demand that a lot of places sell wireless access to whomever is willing to pay for it. If you're lucky, you'll get a good price on an hourly rate or a daypass, but if you're not you'll get reamed on the price of daily access (I remember one hotel I stayed at in Florida that demanded $30us per day for 802.11b access). This has angered some people to the point at which they've developed a way to get their hard-earned money's worth by developing a way that they can share their paid-for wireless access with everyone else that doesn't want to pay exorbitant rates. Part of this also has to do with battles around the United States between the local governments and the big telecom companies that are doing everything in their power to prevent cities from setting up free wireless networks. The project is called Wi-Fi Liberator, and is an open source system that lets you turn your wireless-enabled laptop into a pirate access point. The app is called Liberator, and so far it exists for Mac OSX only, but the principle behind it is pretty straightforward, and it would be easy to set it up on other operating systems with a little work. You need to have two wireless network cards in your laptop, ideally one that's built in and an USB or PCMCIA wireless card. One of the wireless NICs associates with the pay-for-play wi-fi network, while the other puts itself into access point mode and handles traffic to and from other wireless clients. Your laptop serves as a packet forwarder between the two.

Keep in mind that if you set up a Liberator node, you'll have to run a web proxy of some kind like Squid or Privoxy, but those are open source too, and fairly easy to install.

Now, keep in mind that your traffic, if you use one of these rogue access ponits, will be going through someone else's computer, and you won't necessarily know whose. They could be recording everything going through their computer and you won't be able to stop them. Also, Liberator does not implement WEP or WPA, so your traffic will not be encrypted - you'll have to arrange for that on your own.

By default, the ESSID it uses will be "Wifi Liberator", so keep an eye out.