This Autodesk website has links to several services:
Print an AutoCAD Model Through a 3D Printing Service
Here is a document describing how to optimize your models and prepare them for 3D printing. You can print 3D solids, but not surfaces, parts of a block, meshes, 2D
geometry or text.
This is related to the AutoCAD 2009 subscription bonus pack 3 Shaan has posted about.