How to assign a static IP with a linksys WRT54G2?

From what I have found, it doesn't look like the WRT54G2 supports setting static IPs through the DHCP server. Depending on the version of the WRT54G2 you could load a 3rd party firmware such as DD-WRT onto the router to add these features. Here is a tutorial from someone who did it on a WRT54G2.

I agree with @Spooky. I'm assuming that you want to set static IP's for port-forwarding. You can set certain computers using the MAC Address (directly connected to the AP is best-case and easiest).

Or by setting the IP(s) Manually on the computer(s) outside of the normal DHCP Range (ie: DHCP set from 192.168.xxx.100 to 192.168.xxx.250, manually set the IP(s) from 192.168.xxx.50 to 192.168.xxx.99).

EDIT: Even if you set the IP manually, you will still need the subnet mask, gateway, and DNS IP's to connect to the Internet and the rest of your network. Check those settings to see if there is an issue.

I may be completely wide of the mark here, but when you say

When I set a static IP outside that range on the computer that computer is unable to connect to the Internet.

Are you also setting said computer to use a specific DNS server and gateway? It may be worth checking the DNS server and gateway assigned via DHCP and checking it's the same as what you're manually setting.