Citizenship for an illegal

first i came to USA with J-1 visa (April,2007), which was later exchanged for B-2 tourist visa (September,2007), but it also already expired (March,2008). I want to become an american citizen. What are the ways to do it if I'm already an illegal? Or if it's impossible to become a citizen, at least what kind of visa would be available forcitizenship for an illegal me in order to live and work in the U.S. legally? thank you.