Bitrix24: Social Intranet, Task and Project Management, Activity Stream, Online Storage, CRM, Instant Messenger, File Sharing, Calendars and much more!
Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!

I’m currently testing Bitrix24 and what I’ve seen so far is quite impressing.