Heck yeah! The ziploc *freezer* bags will take boiling water in them just fine. Just don't try it with *sandwitch* bags... You should have a cozy (I just use my toque) so you don't burn your hands, and to insulate it for bit if you need to "cook" it for a while.

But don't take my word for it - Buy sarbar's book :

http://www.amazon.com/Freezer-Bag-Cookin...&sr=8-1