For those that are looking for the IP address for the Linksys Instant Wireless-G Access Point (WAP54G), you can find it on page 11 of the PDF file on the CD. Pretty dumb that it's not shown on the setup booklet, huh?
The factory default IP address for the 54G is 192.168.1.245 (subnet 255.255.255.0).
Try setting your computer to 192.168.1.254 (or any other 192.168.1.X address except 192.168.1.245), subnet 255.255.255.0, if you need to connect to a factory-fresh 54G. You'll probably need to reboot, too, unless you're running WinXP.