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.
Logic Puzzles Daily - Logic Puzzles Daily app comes up with features to help you in taking challenges so you can clear levels after levels of brain teasers.
Dropbox - Online Sync and File Sharing
Crossword Puzzle Free - Crossword Puzzle Free is an app by Redstone Games that provides you with a variety of different puzzles according to various difficulty levels such as easy, medium, hard, and pro, etc.
Google Drive - Access and sync your files anywhere
One Clue Crossword - One Clue Crossword app allows users to access an extensive collection of more than 1000 different puzzles in order to exercise their brains on a daily basis.
Mega - Secure File Storage and collaboration