I recently tried and purchased Dropzone 3. See a list of features on the linked official website. In short, Dropzone 3 provides an intermediate zone for drag-n-drop. You can use it as a stash (called "Drop Bar" — stacking is available), use it as a shortcut by putting frequently used folders and applications there, or trigger actions by dropping. There are a dozen builtin actions and an additional list of readily available actions, covering common web drives, SNS and file sharing sites. Better yet, you can develop your custom actions with the easy-to-use Ruby API. For instance, I wrote a simple Google Translate action,
Google Translate.dzbundle (link), based on translate-shell. (You know, it's Ruby, so calling external commands and concatenating strings feel at home, as if you are coding in Perl or directly in shell; unlike Python, where you at least need to
import subprocess then
subprocess.check_output to get the output of an external command, and have to use a bunch of stupid
+'s to get your goddamn message to print.)
Although I use the terminal for most tasks, drag-n-drop is still useful and convenient at times, not to mention the custom actions. (And the stock drag-n-drop is kinda hit-and-miss, especially for people like me who are mostly working with windows maximized — except terminal windows.) After using Dropzone 3 for a while, I found it well worth $4.99.
Wait, I didn't mention the pricing? Dropzone 3 is only $4.99 on MAS, so get it while supplies last. (Somehow the license is $10 on the developer's online store, so definitely buy from MAS and change to the unsandboxed version later — de-sandboxing is free.) There's also a 15-day free trial.