https://wave.google.com/wave It lets you basically chat, do some simple votes, private message, and edit a document in real time on one site.
overview:
[ame="http://www.youtube.com/watch?v=eKUAqNGVwX0"]YouTube- Getting Started with Google Wave[/ame]
This basically lets you Play by post much more organically. So you can write a line of dialogue or action:
"Hey _____________________" - player Gak
and someone else can write a reply in the same document and it will show who is writing it in real time
"oh ___________________" - player Fiz
This basically acts as a one stop place to chat, make posts that anyone can edit. This make things like dialogue, actions, interjections, etc flow much better than they normally do in play by posts.
Also it's super easy to use, just requires a google (gmail) account.