Simple robot, no gearbox.

Here are available a lot of movies and assembly ideas (sorry guys, the text is Romanian, but you can still use the pictures and videos) - http://www.robofun.ro/flexy-bot-mini-4-motoare

You can build it with just 2 motors (here are some videos - http://www.robofun.ro/flexy-bot-mini-2-motoare) with 4 motors (have a look here - http://www.robofun.ro/flexy-bot-mini-4-motoare) or with a lot of motors (12 motors here - http://www.robofun.ro/flexy-bot-mini-12-motoare).