Very interesting - WynnEnvironmental is selling a conversion kit for adding a filter to the (cheap but good) Harbor Freight dust collector:
Let’s see: the Jet canister filter dust collector is $470. The Harbor Freight collector is $150 + $120 for the filter kit = $270.
UPDATE 8/26/2005: I just ordered the filter and some flex-hose. They sound like great folks, very nice and helpful.