Apple don't run this database themselves - it's managed by a company called Skyhook. Given Apple's descent into evil that might provide some comfort to you non-Apple fanboys out there.
Go to this link.
Enter your address and fiddle with the marker to locate it correctly.
Enter the MAC address of your WiFi router - you'll probably need to google the model of your router to do this.
Wait 7 days - when you use the maps application on your iPhone / iPod Touch, hit the center button on the lower left and Boom - there you are.
Will probably help a bunch of other apps that use this data - would love to know what they might be!