I stumbled across a very cool post from Mac Sage.

If you have any Mac running Tiger 10.4 or greater with an Airport Extreme Card or any compatible wireless PCI card installed in your Mac forget running out and buying an AirPort Express Base Station. Like the title says, you can use your Mac as a wireless router.

Check out these easy steps…

If you?ve recently purchased an iMac, chances are that it came with Airport wireless built in. If you have cable or DSL service, but have yet to purchase a wireless router, then you?re in luck. You can turn your iMac into a wireless router for your home or small office. Here?s how:

First, here?s a basic diagram of what is needed. 1) A cable or DSL modem, which typically provided by your internet service provider; 2) a Mac (with built-in Airport wireless) which is connected to your modem via an ethernet cable; and 3) any number of laptops which have wireless capability.

There’s more to the steps click here for them. Thanks Mac-Sage. Great post.