CTRL-X CTRL-E will take you into your editor[1] from the command line, where you can paste away and see/edit if necessary. Once you exit from the editor the commands that were entered will be run.

So (if vi): CTRL-X CTRL-E i CTRL-V[2] ESC :wq

[1] at least in bash, possibly others.

[2] or whatever your paste shortcut is, and then edit if necessary

Edit: seems this is also possible for zsh but needs some config first: http://nuclearsquid.com/writings/edit-long-commands/

Shouldn't have to be a pain? Browser plugin to paste content to editor window. Then something that runs the document its pasted into when you've read it?

However, copy, paste, (save as a script|paste in terminal), run isn't exactly the most strenuous task in the history of man either. So it'd be a fairly meaningless chain of plugins for close to zero benefit.