Dropbox - Online Sync and File Sharing
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.
allTags - allTags is a free, tag based file management application.
Google Drive - Access and sync your files anywhere
Tabbles - Tabbles use tags to organize and find files along with your colleagues.