tom's hardware has a pretty good article on how to build your own computer that talks you through the basics of each component and what to look for. Tigerdirect.com has a very simple one as well.
Also, tomshardware periodically puts out articles called system builder's marathon where they will build different systems depending on target budget and then overclock them to max potential. very useful to see what components they are matching up and what settings they are using to overclock.
http://www.tomshardware.com/reviews/core-2-overclock,2146.htmlOnce you have read through them, lmk if you have any questions.
other useful link:
http://www.tomshardware.com/forum/258512-31-build-computerFinally, you should look at people's rigs in the pc help/tweak forum -- will give you an idea of what kind of components people are matching up.