Joe Kraus, one of the co-founders of Excite, and new blogger has long been rumored to be working on a new wiki tool. Today at the Web 2.0 conference Joe finally unveiled JotSpot, a new type of wiki that they have named an "Application Wiki". JotSpot appears to be not only an advanced wiki, but it also moves the predominantly text-based wiki toward being able to handle structured data and web application development.
The discussion during the demo is also very interesting. Jon Udell made an observation about JotSpot entering into Lotus Notes territory, and Kraus and Spencer discuss how JotSpot makes web application development more accessible, and expressed their desire to create a marketplace for small developers to create tools using JotSpot.
From what I've seen so far, JotSpot looks like it may the first of a third-generation of wikis, the first being the very simple wikis such as Ward Cunningham's C2 Wiki, and second generation being database-backed wikis such as Wikipedia and SocialText. If you are serious about wiki, I highly recommend you take a look at this demo.