I found this cool collaborative blogging site called MemeStreams. Here's their description of what MemeStreams offers:
A democratic view: On the main page you'll find the most popular recent articles on the net according to our users. There are no editors. Everyone's recommendations count equally. These recommendations are organized into different topics so that its easy to find the information you want.
A reputation agent: There can be no tyranny of the majority. As you use this website, MemeStreams takes note of web logs that you find interesting and recommendations that you agree with. The agent uses this information to produce a custom news selection for you which is made up of the most relevant recent articles according to the people on the site who you most often agree with. You can also create specific communities of interest that you would like to follow using the agent.
Threading: Web logs often consist of entries which reference and respond to other web logs, and so on. Unfortunately, these discussions are spread out on different sites and there is no index into them. MemeStreams can present a threaded view of all of the discussion that links back to a URL. This is particularly useful when surfing the web, as MemeStreams can offer you one-click access to all of the threaded discussion for any web based content that you happen to be reading.
Search engine: Search engines are designed to provide the most relevant results, but everyone has different ideas about what is relevant. MemeStreams allows you to see what different communities of interest think are the most relevant results for your search. You can also search a particular weblog, including your own. This is quite helpful when you want to revisit an article you're read in the past.
An inbox for links: You can use MemeStreams to forward a link directly to a friend who might find it interesting. If they are a MemeStreams user, you can send the link to them in MemeStreams. This reduces email inbox clutter by moving web site recommendations into the web.
I like everything about their offering except for the fact that it's a closed system. I'd like to be able to incorporate the features they offer into my current blog. It would be nice to have each of these features available as a web service. Maybe they'll develop an API.