I've just found a piece really cool 3d modelling software called wings3d. I'm using the version for linux and it was a complete bitch to install. If you have linux and decide to compile wings3d yourself, you will need erlang, OpenGL or Mesa, SDL and ESDL. Erlang and Mesa was easy to compile, while ESDL was almost impossible with my limited knowledge of linux. I was lucky enough to find a rpm for it though.

I've started to have a go and making some simple models in wings3d and it's really simple and intuitive. Having used Catia and other engineering 3d modelling programmes, this seems really simple, yet versatile at the same time.