A lot of automotive forums do this regularly, and tech-related forums as well. A manufacturer agrees to provide X numbers of Product X at a discounted rate if enough people are willing to go in together and buy it. For example, they agree to sell a new Xeon headlight package for 40% off if the forum can come up with 50 people to purchase it. The money is generally held in escrow by the forum owner until the group buy has met its goal of 50 purchasers, at which point the money is sent to the manufacturer and the product is mailed to the purchasers. This 'group buy' model is done in lots of different niches, mainly automotive forums, but our niche is game software addons and we will be using it for that purpose (Publisher X agrees to sell 50 copies of a game addon at a reduced rate for our forums members).
This mod should do pretty much everything we need with just a language file edit, but if you were familiar with the concept of a 'group buy' and could add in some cool additional features to support it you would make us happy and probably sell some additional copies yourself. :) One feature that might be nice is a way to let buyers (or contributors in the current version) input some info when they buy/contribute (things like their mailing address in the case of a group buy of a physical product). Another nice option would be an export feature where the forum owner could export a list of all buyers in a certain group buy sale in csv format (along with their name/username/email/address/etc) to give to the manufacturer of the product being bought.
Does that make any sense? If not I'll try again. :)