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.
Dropbox - Online Sync and File Sharing
Xmind - Xmind is a brainstorming and mind mapping application.
Google Drive - Access and sync your files anywhere
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Mega - Secure File Storage and collaboration
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.