The easiest fix is, don't laugh, duct tape. I have a friend who caught an ember on the sleeve of his jacket and he covered it with a 2" square piece of duct tape. It's still going strong for over 10 years now. He washes it with the tape in place.
I personally have patched a hole in a down jacket with an iron-on patch. Set the iron to low and make sure the glue melts. Back up the repair area with a the end of a dowel or something to make sure you get good pressure on the patch with the iron.
These certainly aren't the most sophisticated methods but they work.