[Toadling]

This feature has existed in OmniFocus for well over a year. You can drag a file into the inbox or into existing projects and OmniFocus will automatically create a new action with the file attached in the note field (or drop it on an existing action to attach the file to that action). If you drop the file at the top level of your hierarchy, a new project is created with the file attached in the note field.

However, there is room for improvement (and maybe that's what the OP is referring to). For example, it'd be nice if OmniFocus would respond to files dropped onto its Dock icon. It might also be handy to be able to drop a file onto a project in the sidebar or maybe even have the sidebar folders be "spring-loaded" like the Finder.

But at least the basic functionality already exists. That, along with brianogilvie's suggestion of using the clippings shortcut, has been sufficient for my needs. But I like all my Dock icons to respond intelligently to drags, if for no other reason than it just feels Mac-like. ;-)

-Dennis