I know installing is half the fun, but I was wondering is there any computer companies that preinstall...or optimize their pc's for Linux?

Yep, Here are a few.

Walmart

Monarch computers

http://www.qlilinuxpc.com/

Avoid Walmart computers at all costs. They are usually installed with Lindows, which is a crappy copy of Linux that you have to pay for... what's with that? Anyway, I'm not sure of any sites, but I know there are places that will custom build computers and install linux on them for you.

Eric

There are a lot of places, Dell at one point sold Mandrake computers. Just do a search on google for them. The majority of linux users install them on their current PC's. The only bonus in purchasing a linux computer is the fact that you don't have pay for Windows OS and several windows software bundles like office and anti-virus softwares.