There's a piece of software called 3D explorer that does a good job of converting file formats. I dont think its in production anymore (encompassed within another product) but you can still find a trial version that gives you 30 days to play about with it. I found it useful as it can convert various formats including lightwave files to .3ds which I could then import into Maya (I needed lots of car models and most of the free ones out there were lightwave format).
I found that the best format conversion with that piece of software for models was to convert them and save them off as 3ds format before importing into maya.

Simon