Thanks for the recommendations.
I just don't think I could do the milk-carton solution, no matter how desperate I get for hauling space. Just too ugly. My bike probably wouldn't start, due to the embarrassment.

I'm going to follow up on the links from Susan and Dave, both seem to have some bags I can afford after spending most of my dollars on the bike itself. I don't need any 'show quality' stuff right now, just something to stash stuff in.
Paladin, someday I'd love to pursue the locking pannier option, so keep me posted about how it goes. Lots of places around here (LA) stuff gets stolen before you can even slow down.

Something that locks would be great.
Today I bungeed on a little soft-side pack I scrounged up, and was able to pick up a couple of things at the grocery store and some fabric for my quilting project, and it worked out OK. Where there's a will, there's a way, right? I could have opted to take the car, but where's the fun in that??