For hosting common files it's ok. Also it is on Android too do, great to transfer files between your Windows and your phone. But if you want better security you have to subscribe a monthly offer.
Jostle - A new kind of employee intranet that drives engagement & workplace culture. Achieves social participation in work relevant way. Participation rates are over 85%.
Dropbox - Online Sync and File Sharing
Bitrix24 - 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!
Google Drive - Access and sync your files anywhere
Yammer - Yammer is a leading enterprise social network used by more than 200,000 companies worldwide, including 85% of the Fortune 500, to get work done smarter and faster. Sign Up Today.
Mega - Secure File Storage and collaboration