Need advice for 'marketplace' plugin

Hi fellow WordPress lovers,

I can’t seem to find the right sort of plugin for something we want to put on our site. I was hoping to get some good advice here.

What we’re looking for is a kind of ‘marketplace’ plugin through which users can place ideas for practical projects and request practical help from other users with the same interests and skills.

A couple of ideas have crossed our minds:

• Webshop plugin – but can other users place comments and discuss details with the poster?… And could you hide the price?
• Auction plugin – but same as above.
• Some sort of advertisement plugin where users can post their projects as advertisements?…

Now after a long hard think the conclusion basically is that a simple forum would probably best suited. However, we already have an extensive forum on the site and since starting and completing projects with the help of the community is the essence of the website, we would very much like to give this ‘marketplace’ a special outfit.

So: is there some sort of plugin we haven’t thought about yet? Or is there anyone with other ideas? We would love to here it!

Thanks in advance for any advice in advance!
– UbuntuPlanet.