FriendFeed is a useful way of bringing together many of the second generation web platforms. Once you are signed up you can provides the application with account names for popular sites such as Facebook, Twitter, del.icio.us and Digg, as well as blog feeds. With these details it provides an extremely useful service - it aggregates information provides by these sites. For example, if I comment on a post on Digg it will automatically sync the comment on my feed.
When you think of this in the context of a community it provides a common way of sharing information. Blog posts can be commented on from one site and Twitter comments can be followed up with a single click. Another useful feature is that you can create rooms for various interest groups, helping seperate information. For example, I created a radio room. Feel free to click through and have a look if your interested. Many people are using the site to follow conversations on Twitter - something hard to do with the Twitter alone. Well worth a look if you subscribe to many services and would like to bring them together.