Is there a site where I can enter my credit card/debit card number and receive BTC?
The only one i know and i've experinced with this is buy from virwox.com. You will deposit by your MasterCard/ Visa etc to your virwox account and then buy some Second Life Lindens (SLL) after this step, you can buy BTC from your SLL balance. Now you have BTC on your balance that you can withdraw. Watch out for the fee! 
. So the scheme is VIRWOX -> SLL -> BTC.