Currently, cloud storage integration into Chrome OS is pretty much limited to Google Drive. Sure you can log in to Box, Dropbox, or any other cloud storage system via the browser and upload stuff, but Drive is the only one that's really integrated. However that's about to change. Google today announced that Box integration will be coming soon to Chrome OS. It'll be making its way into a future release of Chrome OS, and users will be able to sign and have access to their Box storage pretty much the same way that you can use Google Drive right now on Chrome OS. Sounds pretty handy, right? Basically, this means that Box integration will be at a system level. Think about it this way, when you save a document or download a picture, you'll be able to download it straight to Box, Drive or your Chromebook's SSD.
For those that haven't heard of Box before, it's more of an enterprise cloud storage system. As they are mostly targeting business users, and have integration with all kinds of apps, including Microsoft Office's web apps. They also offer some pretty decent encryption for their users' files, however one of the big drawbacks of Box is the upload size. While Google Drive allows you to upload any size file that isn't larger than the space you have free in Drive, Box only allows files up to 250mb in size. Which for most, is probably more than enough.
Google hasn't announced anything in terms of when Box integration will be available. But that's not really a big deal these days, as we'd rather have it baked into Chrome OS well, without any bugs, than to have Google rush the integration. Google seems to be getting really serious about Chrome OS lately. They've partnered with Adobe to get Photoshop on Chrome OS and now we have Box integration coming soon. What else will Google add to Chrome OS? Hopefully this will change the perception of Chrome OS. Where most people just think it's a netbook with a browser, yet it's much, much more than that. Especially now.