Google Drive, Microsoft SkyDrive
Now that Outlook.com is open to the public, Microsoft SkyDrive is too, and it comes with 7GB of free storage. I’m already using Apple iCloud (5GB), Dropbox (3.6GB) and Google Drive (5GB), and with the addition of SkyDrive, that makes over 20GB of cloud storage that is available to individual users free of charge… I am loving this.
SkyDrive has really beautiful web app versions of Word, Excel, PowerPoint and OneNote, and the overall interface is extremely nice. If this is what Office 365 looks like, I may have to give that a try too.
Google Drive still has more web applications (formerly Google Docs) and also has, importantly, optional two-factor authentication. I’ve been using the Google Authenticator mobile app for multi-factor authentication with LastPass, and you can easily add Google Drive and other platforms right in the same app.
iCloud already handles a lot of the storage needs for iOS devices natively, including iTunes music; and Dropbox is still the easiest and most intuitve for basic file storage, syncing and sharing.