Dropbox is a great service for backing up files and sharing them between multiple computers. However, with the right tools, you can make it do so much more. Imagine dropping a set of documents into your Dropbox folder and having them instantly converted to PDFs. That’s exactly the sort of thing you can do with Dropbox Automator.
This free service allows you to setup custom automated tasks within your Dropbox folder. Once you’ve decided on what task you want to carry out, you’ll create a folder for it, and then tell Dropbox Automator what you want to do with files put into that directory. You can do things like convert documents to PDFs, upload pictures to Facebook/Flickr, resize/rotate/watermark images, email files and more. There are a few paid services, such as having text documents printed and mailed, but otherwise, most remain completely free.
The only downside to this is that the service will have access to your files. That should seem pretty obvious, since it is interacting with them. It’s just something you should keep in mind, in case you have sensitive files.