Quality aluminum frame kits. I've ordered from them several times. Each frame part is wrapped in brown paper before shipping so they arrive scratch free and clean. Every once a while, I order a bunch of frame kits in common sizes so I can frame most anything I want anytime.

For glass, you could either get some cheap frames from a local discount/closeout retailer and discard the inferior frames, or get a local glass place to cut you a stack. Either source, you'll need to clean the glass well before you use it.