Huge fan of the iron-on denim patch. Repair, reduce, reuse etc. Usually fix-it internal (as above). For the kids used to iron on the outside - until they said stop.
Recently found Iron Patches (great name); bunch of denims, internal/invisible options, brown duck canvas, or thicker tent canvas patches. Made in USA and free shipping. $6.00 for 8"x5". Meant to add... patch yer damn jeans...