I mentioned before that I was playing with some feed aggregating sites. FriendFeed is my current favourite, largely because it lets me create feeds for friends who have not signed up. I accept that they may not want to, but I want an easy way to see what they are up to on various social sites. FF keeps adding features. One useful one was the ability to add multiple feeds of the same type. That's good if you have more than one blog or want to use feeds from sites that are not directly supported.
I've also played with ona*swarm. They use the right technologies, such as OpenID, but nothing else really stands out.
This week I've been looking at Pownce. Kevin Rose of Digg is behind it and it just became available to anyone to register. So far I can't see anything that really makes me want to use it, although they do use some semantic technologies that I favour.
I've used the FriendFeed gadget on my Multiply page. I may use it here when I decide if it's what I want to use 'permanently'. Nothing is permanent on the internet.