How much money do I need to actually buy a home?

I'm not really talking about mortage payments and condo fees and everything that i pay every month, i'm just wondering what I need to acutally put down when I go to buy the house.

I've heard about closing costs and things, but how much do they usually run? How much do I pay my agent? etc. just basically, how much additional money does it take to buy a house (not including the monthly mortgage payments)?