Seems the free Meshlab can read all these formats or other and make also more things :) http://meshlab.sourceforge.net/
sure it's not a "real viewer" but result is the same :)
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Pilou
Is beautiful that please without concept! My Gallery
Hi Michael T - well you could send whoever you want to view your model a link to the MoI "no save" trial version which they could then install and use to open up your main 3DM file.
Or probably the trial versions of various different programs might work, like you could use the trial version of Silo (http://www.nevercenter.com/silo/) for an OBJ viewer.