Not as easy as Dropbox, but offers 7Gb storage.
Free iPad app: http://itunes.apple.com/us/app/onedrive/id477537958?ls=1&mt=8&uo=4&at=10l6SU
Free iPhone app: http://itunes.apple.com/us/app/onedrive/id477537958?ls=1&mt=8&uo=4&at=10l6SU
Free Mac program: https://onedrive.live.com/about/download/
Free Windows program: https://onedrive.live.com/about/download/
Website: https://onedrive.live.com/
Google Chrome app: https://chrome.google.com/webstore/detail/onedrive/nffchahhjecejoiigmnhhicpoabngedk
Free Android Phone app: https://play.google.com/store/apps/details?id=com.microsoft.skydrive
Free Android Tablet app: https://play.google.com/store/apps/details?id=com.microsoft.skydrive
Easy to use, but allows only 2Gb storage.
Free Android Phone app: https://play.google.com/store/apps/details?id=com.dropbox.android
Google Chrome app: https://chrome.google.com/webstore/detail/ioekoebejdcmnlefjiknokhhafglcjdl
Free iPad app: http://itunes.apple.com/us/app/dropbox/id327630330?mt=8&uo=4&at=10l6SU
Free iPhone app: http://itunes.apple.com/us/app/dropbox/id327630330?mt=8&uo=4&at=10l6SU
Free Mac program: https://www.dropbox.com/downloading?os=mac
Free Windows program: https://www.dropbox.com/downloading?os=win
Website: https://db.tt/dUahryRn
Create collaboratively.
Free Android Phone app: https://play.google.com/store/apps/details?id=com.google.android.apps.docs
Google Chrome app: https://chrome.google.com/webstore/detail/google-drive/apdfllckaahabafndbhieahigkjlhalf
Free iPad app: https://itunes.apple.com/us/app/google-drive/id507874739?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/google-drive/id507874739?mt=8&uo=4&at=10l6SU
Website: http://docs.google.com/
Can us as a Wiki, with multiple authors.
Website: http://sites.google.com/