Lay a peice of bread on top of a lampshade. Light the light bulb. Any bulb will at least warm the bread, and larger ones will toast it quite nicely. Butter it or jam it if you got it.

Oh. Yeah. Keep an eye on it, and it's best to use a lampshade with a hole in the top SMALLER than the peice of bread.

You can use a lightbulb to warm a lot of things.