Easy out and a new bolt. Don't just drill the bolt out, unless you're willing to retap at a larger size.
http://www.toolprice.com/category/screwextractors/
Don't just drill the bolt out, unless you're willing/able to retap at a larger size.
And what's with people breaking seatpost bolts? Ease up a bit, assuming you're seatpost is the right size you should have to torque them down that much.