How can Buildings be Made Fireproof?

In the real world having something taller than your house is the way to do this, so in Minecraft you could build a spire next to your house.

However, unless Notch has implemented lightning "properly" you won't be able to rely on this, and your only solutions are to put something non flammable between your house and the sky or build out of non-flammable materials.

The only real alternatives to stone are brick, gold, iron (but these depend on you being able to find a lot of clay, gold ore and iron ore) and glass.

I'd try a glass canopy in the first instance.

As long as lightning doesn't travel sideways, just build a fireproof roof and make sure there are no trees immediately adjacent to your flammable walls.

Using stone half-steps is a surefire (ha!) way of making it lightning-proof and it makes it not quite as unsightly as having full blocks like cobble or regular stone.

Glass would be another alternative, though less desirable in my opinion.