I've been using Plupload for years with great success. But, in most cases, I use it in a one-to-one context. Meaning, one context, one uploader. While this works, it requires the user to stay in the same context while the uploads are being performed. As an experiment, I wanted to see if I could break that paradigm and use a single, global uploader. Then, in each context, rather than creating an actual uploader instance, I create a dropzone that "hooks into" the global uploader. This way, the user can move around the (Single Page) app while the selected files upload in the background.
In this AngularJS experiment, I have a global uploader and two different sections. Each section has its own dropzone that sends files to the global uploader. The user can then navigate between sections while section-specific files are being uploaded.