Well, I'm now deep in the search for an open source project. Here's what I'm thinking about - VoIP Peering. A VoIP Peering and Interconnect BOF was held last month at the IETF meeting, and from what I hear, there was real involvement from the carriers. It's pretty clear (I think) that, in the long term, carriers MUST use IP peering when available because of cost reasons. Never mind what this means for the large amount of IP services that will follow afterwards.
This sort of goes with something else I'm thinking about - the principal of end to end transparency in the Internet. One knock against session border controllers is that they break the transparency rule in the Internet.
So, given that peering will be done over IP, but today's SBCs break transparency rules, what I'm thinking about is leading an open source effort to make an Open SBC. This Open SBC will follow a route more friendly to the IETF, and concentrate on executing policy between networks, establish authentication and encryption, maybe help with media routing and try to find some way of doing all of this without breaking the transparency rules. Or at least, as few as possible.
I feel like Pooh bear walking around, scratching his head saying "think, think".