The founders of Nuvvo have called it quits. See details here.
Techcrunch talks more about it here.
On a personal note, I believe very strongly in what all of the Web2.0 Learning companies are trying to do. However, everything about "the new web" is about Learning. And while I applaud every effort in this space I'm not sure how to monetize the learning function in the commercial market. I don't have any idea.
Google is held up as the single greatest learning tool that ever existed (here). Wikipedia is a wealth of knowledge...good, and accurate knowledge despite what the reports say. Open Source wikis and blogs are becoming internal goldmines of information...especially since they are on servers in a format that internal search systems can crawl and index.
Of course, I'm speaking from experience inside a giant corporation, and many of the web2.0 learning apps are focused on supporting small and medium sized companies. So perhaps there is a market, and perhaps there is a business model that works. I'm keeping my fingers crossed for the guys that are still out there fighting the good fight.