BlackBerry has already included integration with DropBox and Box.net at launch with more partners coming. Until then Innovatology has released a BlackBerry 10 version of their slick Files & Folders app for BlackBerry 10. This app gives you not only access to the files on your phone but also Dropbox, Box, Google Drive, Google Docs, SugarSync and Microsoft SkyDrive.
I tried the BlackBerry 10 version of Files & Folders and I have to say I am impressed. The app is fluid and works beautifully on BlackBerry 10 with a Cascades overhaul. Now if only they could find a way to tie these services back into the native file manager.