For information on making a flag, you can click on a Quiltville post. There is an effort to collect flags similar to what was done for the To Boston With Love.
The link to the Canadian site, which you can reach from Quiltville post, is in French! The flags are due August 24th, so the deadline might be a bit too tight if you haven't already made your flag. I hope mine gets there in time!
I used Jacquie Gering's great heart tutorial. I cheated a bit. She sewed together strips of fabric to make the heart. I used a striped fabric instead! I also made the heart smaller to fit on the flag.
Detailed information on the tragedy is found here: http://en.wikipedia.org/wiki/Lac-Mégantic_derailment