I use this in my Harbor Freight cabinet. About five bucks a bag here. Medium coarseness
http://www.quikrete.com/ProductLines/SandCommercialGrade.asp
I also replaced the siphon tube and gun with this kit and it made a world of difference
http://www.tptools.com/USA-Cabinet-Gun-and-Pickup-Tube-Upgrade-Kit,2320.html?b=d*8026
Works very well for general blasting. Just make sure you use a shop vac with a bag as the silica is bad for you to breath. I've thought about setting up a 5 gallon bucket as a "reclaimer" as it does pull some media out of the cabinet.
