Who's using it: Teachers and students sharing notes, co-workers jamming on shared projects, friends sharing lists, notes and recipes, and individuals jotting ideas for themselves to tap on the go. So far, more than 42,000 PBWikis have been created.
Who's behind it: Three Stanford grads in their twenties with wacky creative cred ranging from host and creator of all-night developer party hackathons (at his own house, no less), blog owner of WillTeachYou-HowToBeRich.com, and creator of geek hit T-shirt "You have died of dysentery" (refers to old Oregon Trail computer game-yes, that geeky.) No doubt smarter than your average entrepreneurs trying to make money on Web 2.0.
How do they make money: There is a free version (and you can create as many as you like, as long as you don't abuse the system), but also a premium one with better bells and whistles at a cost of $5 per month.
Why should you care: Besides being a useful personal tool for collaborating-and creative types always (pretend to) love that-the collective idea of wikis is evolving. Instead of the free-for-all, easily editable (but also spamable) wiki Web sites of the past, real organized and collaborative thought is finding a semi-public home on the Web through these kinds of tools. Wouldn't it be great to be part of THOSE conversations?