Our distributed team uses an instant messaging tool, in our case Sametime, to stay in touch throughout the day. Unfortunately we have a few folks who are behind a firewall and can't join us on Sametime and for those folks we currently use email or if an emergency, cell phones. We also have company-provided Sharepoint tool for online general information, editing and archiving product deliverables, etc. Plus a company-provided web meeting/conference line for all of our meetings. We use a wiki for technical information discussions among ourselves and with the client. We are still learning how to be the most efficient. We have talked about but have not used any of the tools for face-to-face communication.
In addition to the above: a tool for sharing the sprint backlog and tasks to do/in progress/done, like ScrumWorks.
We use either trello.com or icescrum.org (cloud solution).
trello is really useful for "short" dev (let's say less than 5 iterations).