Autodesk Beta Programs has posted a few open enrollment beta programs called eBetas. Of course it must be considered these are unsupported and unreleased products. They will also require that you accept a non-disclosure agreement.
Posted enrollments:
* AutoCAD Electrical
* AutoCAD Mechnical
* Mechanical Desktop
* Autodesk Express Viewer 4
and soon to be released for enrollment:
* Autodesk Inventor 8
The links and details are provided on the eBeta page
of Autodesk Beta Programs
http://betaprograms.autodesk.com/betaweb.htm
Have a great weekend.
Cheers,
-Shaan