Dion Hinchcliffe has a nice rundown of the best web 2.0 software of 2006 - though the list is largely sites broken down into categories such as social network, start pages, social bookmarking, peer production news etc. Still, it's software that enables these sites, right?
Myspace is an interesting example. Their software is cruddy, and strictly speaking they're not a content site, but it is a genius marketing operation.
There's some great stuff on Dion's list. And it's going to be fascinating to watch where they go this year.
According to Techcrunch there has been a fair number of additions to the DeadPool list of web 2.0 start ups. But that's to be expected.
My tip is 2007 will see an upsurge in useage as more and more of these sites go mainstream outside of US based demographics.
It's an exciting time to be working in this space ...