I like DoGA CGA (L3 is the latest.) It uses a parts metaphor where you pick pre-generated models from a "parts bin." You can then scale, rotate, and texture them as desired. It is very easy to use and specifically geared towards mecha like spacecraft.
Check out
http://www.doga.co.jp/english for more info.
Oh yeah, it's free although you can register it in order to make AVIs or to just support the team.
--
TAZ