Axles and Alloys is a miniatures-style wargame played with Hot Wheels and similar sized vehicles. It was developed by Owen Cooper of the U.K. as a free gaming system for those who enjoyed modifying and playing with old Hot Wheels cars. The game is now in development by several fans of the original, and new rule sets pop up online every few months, as well as pictures of people's converted vehicles. This page covers hints on finding materials for the game, modelling tips, and some example cars.
Other related sites:
Blert.net - Axles and Alloys pictures and rule sets
Rogviler's Library - General wargaming site with Axles and Alloys coverage