Recently my Mum got a fancy new television with internet connectivity. This requires either a wired ethernet connection or a brand-specific wireless dongle which costs an additional $100. The TV location is not suitable for ethernet, but a wired connection can easily be provided using any old laptop with WiFi. I've previously posted how to use Windows XP's Internet Connection Sharing for achieving this, but I've since switched to a much better solution.
Network bridging, whereby disparate networks are logically joined, is a standard feature of Windows XP. In our case we bridge a wireless and a wired network transparently. It's very easy to set up, as described concisely by Microsoft, or in more depth by Home-Network-Help.com.
After the network bridge has been created on the laptop you can leave it enabled. The laptop will continue to function as before, but with the bonus that wired internet access can be provided to any device simply by connecting an ethernet cable from the laptop to that device. No further configuration is required on the laptop for each new connection. However, remember that if you need to tell the device that it has network connectivity then it is a wired, not wireless, connection that is active.
As an aside, the internet features of the new television, Facebook and Shoutcast, were not very useful, so a more permanent connection will not be required. However, if it had been, I would have purchased a $30 multi-purpose wireless router rather than an expensive brand-specific wireless dongle.