Twitter: Where Nobody Knows Your Name
kara.allthingsd.com
kara.allthingsd.com
Nothing.
FriendFeed? Same deal. Most of the people I've found have been from the public timeline or from HN. Only a few early adopter types that I know from work are starting to show up on Twitter and most of them never post--probably just checking it out.
I tell people "it's like asynchronous instant messaging with programmability and succinctness rules." I guess I'm not selling it right because that doesn't get much rise out of most people. FriendFeed is easier to explain, but a vast majority of people I know aren't at the complexity stage that makes it valuable. I'm not really there either, yet.