rough guess for what you listed, $600-700.
check out newegg
for pricing, etc. tigerdirect also has some little tutorials on building sprinkled about, that can be handy.
for a thorough intro to building a system, check out the pinned topic "system building information" at the top of this forum.
I also reccomend reading some reviews of equipment you are considering. I am partial to tomshardware.com
, as they offer extensive reviews of many many components, and good comparisons.
two things to remember- spend a few extra bucks for a good quality power supply (psu). 480 watts+ by antec, thermaltake, or enermax will last through the next few upgrade cycles, and provide rated power on a consistent basis.
also get quality ram, preferably in a dual channel kit. when you pick a motherboard, look at their list of compatible ram, you wont go wrong with something they list.
you will also have to decide between intel and AMD. either is fine. the amd monkeys will surely be posting about how much better they are for gaming and overclocking. go with whatever your comfortable with.
more questions? let em fly, we like to help!