3D System modelling tool?

Hi guys,

Anyone know of a 3D graphic display/builder for modelling a solar
system?
Yes, I know it is 'easy' to search the web for one. Tried that already
and
came up with a bucketload of dead links or programmes that are either
not
easily used or don't allow a 3D representation.

So if anyone has come across one we would muchly appreciate a pointer to
where we can find it.

We intend using it to support a 'mini-campaign' we have just commenced.

Cheers,

Owen G