Good luck.
My only recommendation is to not be fooled that you can turn a profit building custom machines for people unless you are doing some super-high-end custom stuff. Dell and the like are just too cheap these days to make money building boxes.
As far as businesses go, OS deployment and monitoring are very hot right now as well as web collaboration, so check out SCCM/SCOM/MOSS if you're interested in doing Microsoft platform consulting.
Good luck to you.
-Steve O