Is there a file sharing service akin to Dropbox or SugarSync that would offer an API? I would like to add a file sharing service to a website, but the full Dropbox interface is still too complicated for my users, so that I’d like an API to build a dead-simple list of files integrated to the website. There is a Dropbox API project on Google Code, but it seems to be dead.
Update: I need a service with a desktop client at least for Windows, so that the more technical website users could easily upload and organize the stored data. Extra points if the service has a free plan.
A quick search on ProgrammableWeb brings up about 50 API results.
Out of the lot, I could only say that I have had experience with the Box.net website. I've had no trouble in the past, and they have rather acceptable limits for the free account (25 MB per file; 1 GB of storage).
I'm sure that with a little poking around you'll find something that fits your needs, but I wouldn't expect to find something that offers you a business-scale solution for free, you might have to be prepared to make an investment, and in that case some of Amazon's Web Services might be better suited to your needs.
Edit: Since I answered this question 6 years ago, the landscape for storage solutions with APIs has changed somewhat. There are now free or affordable services with mature developer APIs offered by Dropbox, Google Drive, Amazon S3, Rackspace CloudFiles, Microsoft Azure and for mobile, iCloud.