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
HEY - Email at its best, new from Basecamp.
Google Drive - Access and sync your files anywhere
InstAddr - Disposable email address application.
Mega - Secure File Storage and collaboration
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.