[googletazer]

Ads for affiliate products corresponding to the event could work, e.g. high quality (cannot stress this enough!) products from Amazon. Say, for paintball meetups it would be accessories/clothing/etc... This creates a win-win-win situation - the visitor gets a recommendation for a high quality product that is relevant and they may be interested in, you get a 4 or 8% from each sale, and the amazon seller gets to make a sale.

[funtober]

I think affiliate relationships will be our next test but haven't pursued because our visitors value experiences over merchandise. I was hoping an entrepreneur would setup a ticketing affiliate in our niche area but alas I may have to do it myself.