Are you in a state with legal MJ? If not, finding a place in the US that will ship to you might be tricky.
From outside the US I can personally reccomend marijuana-seeds.nl Unfortunately you'll have to do a wire transfer or money order as they don't curently take any credit cards. (prepaid or otherwise) Regular sleath shipping is $9.95 and guaranteed stealth shipping (one resend if stopped) is $15.95 I think. plus they have a decent free seeds offer with every order.
I picked up 10 THC Bomb Reg., 10 Thai Stick Reg. and 10 White Rhino Reg. for $98.81 and got 5 Sensi Kush + 3 Northern Storm Auto Fem's free.