Hello, 3Dconnexion corp sells some 3D mouse devices. There are 4 different 3Dconnexion devices : http://www.3dconnexion.com/buy/shop.html
Those devices use a proprietary driver but an free alternative is available on : http://spacenav.sourceforge.net/ The problems with proprietary driver are that it proprietary, it GNU/Linux/32bits (Redhat, Suse) only and it only works through the X window system with motif for presenting a configuration GUI (and cannot be made to start without it). I write on this list and hope someone can test these devices on Gentoo. My overlay : http://git.overlays.gentoo.org/gitweb/?p=user/aluco.git;a=summary contains a blender ebuild with useflag 3dmouse. This useflag depends on libspnav and spacenavd daemon that provides free alternative of the proprietary driver. The ideal would be to test each product. Please, feel free to send me reports on my personal mail, I reply quickly. Regards, Anthoine