Plurk - micro-blogging and mood network. One big difference is your stream is a horizontal timeline, you can start your post from a menu of actions eg. “thinking….”, (Jaiku has icons instead) and similar to Pownce you can organise friends into cliques (for more private streams). Like Jaiku and the others comments are threaded with the item…and like Pownce you have fans and friends. It’s also on the mobile web.
Chatterous - a multi format group chat similar to Swarmit, send and receive a message using any of the following SMS, IM, email, and web.
eg. send an email and friendA gets an SMS, friendB gets an IM, etc…