This post on improving markets for social ideas mentioned InnoCentive - an online marketplace connecting people with ideas to institutions that can make them real (in both social and commercial spheres). The CEO of InnoCentive just added a comment, which you can read here, but he notes two things they are working on:
"First, in the next few months, we will be introducing flexible discussion boards to some of public areas of our marketplace, including the ares that serve Foundation challenges. We would actually encourage you and the community to utilize the discussion boards to discuss and make known needs and resources. While not exactly a "Craigslist" taliored to your need, feel free to use the boards to the extent it is helpful.
Second, we have been thinking through models that have the potential to match funding sources with ideas with "solver" community. No promises here, but within a few months we should have a stronger position on this."
This is exciting and I'll try to keep an eye out for more as this develops. I just read of another such marketplace coming online, called Planet Eureka. This looks purely commercial for now. And don't forget other related resource, including socialedge, Kluster,* and Social Innovation Camp. Still not quite the fiscal agency matchmaking service I was thinking about, but now there are plenty of platforms to use to match your great social idea with an existing organization that can make it real.
*Kluster just launched a KlusterNews site. You can see the Kluster founder explain the lessons learned, "Seven weeks in and a million dollars down the drain, we know what works," founder Ben Kaufman said in a video he posted to YouTube." Quoted on CNET.