The best way I've found to removing the broken crank bolt (Last go around was my 3rd time) Use a dremel (the hand held drilling machine...) and they sell a Dremel Bit at Lowe's that is the best $10 I've ever spent - Bit # 9910. It's made of carbide and cuts great.
Just get on the middle of the bolt, and let it do its thing. I usually use WD40 to clean and lubricate the work area for it cuts like no other! The lubrication is used to clear the shaving and to keep the bit from loading up.
Once that is done use an easy out and it will twist out with no hang ups.
At Advance Auto Parts you can buy a Set of Easy Outs...its like a 5 piece set that has 5 different sizes...I beleive the smallest size bit works perfect with the diameter of the hole you drill. Hit it in the hole with a hammer so it locks in and then turn it out with a wrench.
Again 3 times and its worked EVERY TIME. It's slow work, but be paitent and it will work, and will come out.
-Tim