Slack
Slack it's a very convenient tool for team work. It comes with a number of useful features, but the one we should be using most it's the online chat. It saves logs which can be read at any time (so you don't have to be online all the time not to miss things), desktop notifications and Android/iOS apps. It can also be integrated with a number of tools such as GitHub (to notify in channel when something has been pushed).
Everyone in the People page have been invited.
And you can request an invite by sending filling out this form here