Micro Blogging Web Site Mods

My micro-blogging web site needs to become an event blogging web site. So I need an event form (like the one on Helios [login to view URL]) so the a user's message will be to tell his friends about the party or place he is going to by listing that information in the form. The user can already create a friends list. But I need the user to be able to create multiple lists so they can have different groups of friends and then they will be able to send messages/event alerts to different groups of people.