While at the Woodworkers Showcase in Saratoga Springs today I saw something that was rather interesting... On display was a cyclone unit that sits on top of the steel trash can and hooks up to a two bag dust collector. I spoke with the vendor about it a bit and thought it was rather interesting. Thus I figured I'd mention it here (I've got NO connection to the vendor). The vendor mentioned he had them listed on e-Bay so I looked them up.
The assembly has low headroom requirements as there is no blower on top and there is no space between the top of the can and cyclone.