If you've been having trouble with your wireless signal the culprit might be interference from other wireless routers in the area. WiFi Stumbler will show you which channel is least likely to cause interference.
WiFi Stumbler uses your computer's WiFi antenna to scan local access nodes. You can do a wide open scan or narrow it down by the type of encryption, the manufacturer, the radio type, frequency or channel.
When you're done with the scan you're presented with both a detailed listing and a chart showing the number of nodes. Using this information you can then switch your router to a less occupied channel — every router I've ever purchased has been set to Channel 6 for some reason and just getting it off 6 has been a huge help in every instance.
Have a favourite tool for tweaking your Wi-Fi? Let's hear about it in the comments.