I would say that great way to monetize your forum is kontera and google ads. I think it should be great.
Create a VIP section, or differentiate memberships(Diamond,Platimum,Gold,Silver). Charge the VIP a monthly, semi-annual, annual, and lifetime subscriptions. Also offer the VIP significant discounts on any products/services featured on your home site.
I've worked for a subscription based forum that pulled in millions of dollars per month using this model. But instead the content that was generated was so good, that they just charged everyone for access.