I've got plans to use some 300rpm gear motors with a stall current of around 9A. I've been looking around at how to control them and some of the methods available are pretty pricey.
My initial plan was to use four chunky SPST relays I salvaged from work. Number one, they're enormous. Number two, they're relays. I have them and I'll use them if I need to but would rather not.
I found a schematic that uses MOSFETs in its design but I can't find it on google here at work. I have it saved at home. I'll add it later. I'm partial to it as the designer has actually made the thing and has a youtube vid to prove it. Should cost ~$10 per H bridge.
edit- Here's the schematic:
The webpage for the circuit is here.
If there's any other cheap DIY techniques you'd like to share, I'd like to hear about them.