My favorite collaboration tools are in person discussions, online chat tools such as Skype or AIM for quick discussions. Ecahanging Excel Pivot tables that is generally transformation piece of the collaboration process. I hope this helps! Thanks.

I posted the same question on LinkedIn and got these replies:

"Jive SBS, Lotus Connections, Sametime, Quickr and Yammer." John Schwiller

"I've utilized Google Enterprise Apps to great effectiveness for globally spanned teams. This include voice, chat/im, spreadsheets, documents, presentations, video, websites, wiki, etc. The realtime aspect of everyone seeing everything change in real time was powerful. Further, we were able to share, as required with the client base, thus dramatically reducing communication efforts." Don MacDonald