I guess you've probably already read the news that Google is giving
away a trimmed down version of SketchUp. But, in case you haven't:
Interesting that they're not requiring registration and they're
providing an online, searchable 3D model database that you can
up/download to/from. There are already a few thousand models up - sure
would be handy when you want to pop something into a model or rework
one that you found.