Generally, spray foams are pretty expensive, and are used more frequently on surfaces within the space rather than on the ductwork itself. Sometimes you will see a fireproofing spray on I-beams and ductwork, but they don't do much for the efficiency of the system, or noise attenuation.
Nonetheless, the standard for spray-on type insulation for years has been K-13...
http://www.internationalcellulose.com/home/products/k-13/
If you are interested in general plenum liner board, or duct wrapping (lagging) I would check out products by Knauf or Johns Manville
Here is some typical lagging that might be used for general HVAC applications.
http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_friendly_feel_duct_wrap.aspx
edit note: I usually reference these products for commercial applications, but I would imagine you could find stuff very similar at the local HD.