We've just released our HTML5 Cloud File Manager App for the Playbook for which it was designed, although it works with other webkit browsers. It can support access and management to over 35 storage clouds and SaaS services and enables unification of different cloud content, cross-cloud file search, and ability to upload and view documents within the browser.
A free smestorage account is required to use the App, and a free account comes with the ability to add 3 clouds plus 5GB of storage that we provide foc.
So I have played around with this and it is really good. I signed up at : SMEStorage :: Pricing
Get you 5 gig plys ability to sync 3 other cloud services.Hooked up my Dropbox and Box accounts. The html5 app (mobileSME Storage :: Log In) works well. The desktop interface also is nice.
Great way to get all your clouds accessible is one place.