Team Task Server

ARTIS Team Task is a peer-to-peer (P2P) application using Rendezvous to share tasks, ideas, and to-do's.

It takes task organization to the next level by enabling users to send notes, tasks, or reminders to everyone in their team.
ARTIS Team Task Server is a server application using Rendezvous to store tasks for users who are offline and forwarding them when they come online again. It works much like an email server, but for tasks.
ARTIS Team Task Server itself is free, but to create user accounts 'server user licenses' have to be purchased for US$ 12.95 each. The free server comes with two unlimited evaluation server user licenses.