Routers
Linksys
BEFSR41 is a 4-port 10/100 megabit Ethernet router that is widely used and simple to set up and administrate (and my favorite for home use)
If you decide to update the firmware and the update does not complete successfully, the router will become about as useful as a paperweight -- unless you reload firmware. Fortunately, it is possible to recover from a failed firmware update by using the TFTP utility from Linksys (a Windows app found on the Linksys support page for the BEFSR41 router, under the download options for hardware version 4.0). To use this utility to reload the firmware, do the following:
Connect your Windows system to the Linksys router in question;
Manually set your IP information as 192.168.1.50/255.255.255.0 (the rest doesn't matter);
Ping the router (192.168.1.1) to verify that you can reach it;
Run the TFTP utility to (re)upload the firmware (the default password is 'admin').
Software tools
WiFi
inSSIDer (for Windows XP/Vista/7) is a free WiFi network scanner from MetaGeek.
Wireless Wizard (for Windows) is a WiFi spectrum analyzer / tuning tool from AzulStar.