Jaiku’s main goal is to bring people closer together by enabling them to share their activity streams. An activity stream is a log of everyday things as they happen: your status messages, recommendations, events you’re attending, photos you’ve taken – anything you post directly to Jaiku or add using Web feeds.
Chatterous has this to say about themselves:
Chatterous is a service that lets you talk to your friends across the web, im, email and your phone. Once you create a group, you can chat with your friends through im, email or your phone. No need to use the website! Your friends don’t need to sign up to chat with you! They can reply right on their im, email or phone. Once you’ve created a group for your friends, everyone in the group can reach each other whether they’re on im, email or out and about on their phone. You don’t have to install any software! Just use your existing im client, email or phone!
It took me a while to become a Twitterer, so I doubt that I’ll join up to any other service anytime soon. If you don’t Twitter then Jaiku or Chatterous could be the thing for you.