Epinions: Range Hoods

Consumer-generated reviews, buying tips and advice, ratings, price information, and searchable in a variety of ways from price to product type.
http://www.epinions.com/hmgd-Large_Appliances-All-Range_Hoods

Air Cleaning Devices for the Home

Discusses general air cleaning filters and devices, including a small section near the end on ductless range hoods; from the California Air Resources Board.
http://www.arb.ca.gov/research/indoor/acdsumm.htm

ImproveNet: Range Hoods

Lists major manufacturers, product lines, experts, and some how-to and consumer advice, so that consumers can see what is on the market. Does not accept payments for listings.
http://www.improvenet.com/ext/productshowcase/PS_3.html?CID=433