I've never really looked but often wondered if it was possible. I'm sat here at work all day, about 2 out of the 5 days in a week I don't really have a great deal to do, with ?????????9000 worth of software sat in front of me....
I could be sat making 3D's for my rides, but as yet I've not found away to get them into NoLimits. [V] Perhaps I'll go look around the net for a bit, I'll report my findings back here later! [:D]
EDIT:
You could try this:
http://www.sycode.com/products/3ds_export_iv/index.htm
I haven't tried it, but you could give it a go.
Also, I know that you can export Inventor files into Step and IGES files, and I know that you can do a lot more with those file types than you can with the standard Inventor .iam .ipt .idw part files. If you have a program like E-Drawings for exmaple? That's a free program to download and you can do a lot of exporting from that with Step and IGES files, 3Ds files might be one of those possible exports.
EDIT2: I tried the program in the link posted above and it works, it's just a trial however, so you only get 10 conversions. It's $195 to register it perminantly. Looking around the net some more, it's the same story everywhere. It looks like if you want to do it, you're gonna have to buy a software add-in. Or.... you could.... download it from somewhere... where.... you might not necessarily pay for the things you download...? If you catch my drift?