One thing I see pretty often is people asking where to get sensors, lights, etc... I think a category in the forum for deals people might be interested, and a wiki page with "everyday" links to stores selling them and general statistics relevant to the type of product. Some of it comes across in the Tested Sensors category but I think a dedicated area would be best. Heck it may even interest companies to offer deals, or help people sell/trade items they no longer need.
I somewhat picture aspects like that on ReefCentral.com and their sponsors (although sponsors is not an option but you have to think some companies are interested in Almond+ and it's user base/potential customers).