Okay, because it's even simpler than the one mentioned above, I'm testing this one first! : )
It works so far on:
Yahoo Mail's Sign-Out "News Rotator"
ComputerWorld's drop down menus
IT World Live "scrolling feeder" (but not their drop menus, they seem to be something else and are still very large!)
Lots of stuff on DenverPost.com
Fark.com's yellow drop down nag "feed our squirrels"
Rawstory.com's "Like us on Facebook" Right-Left Slider
Wxyz.com's black "switcher menus"
ArgusLeader.com's big blue drop menus.
NY Post's big drop downs from arrows.
(Found another one) Intl. Business Times ibtimes.com
Does not work so well on:
Uproxx.com's color changing menus
Hypervocal.com's huge dropdowns
Tip: Tends to block the video news of new sites, so if that's what you are actually there for, caveat.
((I plan to edit this post a few times as I amble across the web.))
So the other suggestion has a few more buttons, but it's on hold for a little while until I see a "killer" that this ittybitty addon doesn't catch.
Summary for today: So the basic concept is what I was looking for - it seems to eat about 80% of the worst stuff.
And Yahoo Mail seems to mostly still work with it on (at least the old style). So I don't have to toggle it off that many times just to check mail.