I'm not sure how I found ning.com but it's kinda of cool !!!!
On first glance you think. OmG they have gone way over the top on the ajax stuff here, but then you get used to it. The ning team refer to their site as a playground, which basically means it's a place to play with their ajax/php core. The big difference with ning appears that anyone can sign up clone an app and start using it. I've been playing with the blog tools: stupidlist.ning.com & wishlist.ning.com which as you can see are the same thing, but with a different focus.... both of which are very similar to del.icio.us
The extendability of ning looks endless, there are example apps for photo diary's and discussion boards, I really think it's turn its hand to a good help desk system, maybe you'll see one on calcylator.com ;)