Alf releases the code for HeadCloud, and provides his best description so far of the ridiculously easy thought sharing service it enables:

HeadCloud is a Napster-style service, where people connect to a central hub, send a list of the thoughts they want to share, and search the database of other people's thoughts to see who they want to connect to. It's called HeadCloud after the original vision - being able to walk down the street and see little clouds above people's heads that showed what they were thinking.

I haven't gotten around to using it, as I have yet to embrace Instant Messaging. (Gosh I feel old.) I could see it being useful for a tribe-sized cluster of users who already know one another, though. For instance, it lets you think out loud about a movie that just came out and that you're curious about; if someone else happens to also care (e.g. has seen it/is thinking about seeing it), the two of you can connect easily using the title as a bridge. Hey, (paging Stuart...) something like this might come in handy for Skypers, too.