http://www.dict.org (DICT protocol)
I plan on implementing a stable API of some sort; if this or some similar protocol catches on, it shouldn't be difficult to write a gateway server between DICT and WikiAPI. But I don't see much need for that yet until we have a resource worth fetching that way, and I think that's still a year or more away.
A other project that is very alive to think about is http://freenetproject.org
Ah, yes, my previous free time sink (I was involved in that project early on--I wrote the FAQs and such).
I don't think Freenet as it is will catch on--it's not really that great a protocol, and some of its fundamental problems aren't fixable. But I /do/ think that a peer-to-peer distributed database might be an interesting back end for Wikipedia someday. But again, I think it needs to develop in a centralized way for a while before risking that. I may be labelled a heretic for saying this, but part of what make Wikipedia great is its /lack/ or freedom and universal participation. Everything2 showed us what that devolves into. We have a central goal here--a narrow focus, and people to keep the masses pointed in the right direction.