The Howto Forge has a detailed article explaining how to setup a wireless hotspot on a LinkSys WRT54G router. You may recall from a previous post that these particular LinkSys routers are well known for their ability to run various Linux based alternative firmwares. This how to is a perfect example of these LinkSys routers can be modified for a variety of tasks. The wireless hotspot setup in the article is great for offering a free or paid Wi-Fi service in a public place, where users must login first to receive internet connectivity. This is the same type of service you come across when accessing internet at an airport or hotel. Michael also has a great post discussing the WRT54G loaded with DD.