Most of the time, when I was looking for something to throw in because I was too busy to draw up were encounters with maps I could throw out in case the PCs explored somewhere I did not intend. Simple things like a few hook ideas, NPCs ideas, etc. A good DM keeps a few of these around to keep a step ahead. Even if it is not used whole, just to have filler.
That's the idea! I was also thinking about mini-crawls that the PCs can find on the side of the road (like in Skyrim) or other very short adventures ("find my cheating husband please - oh wait, that tramp is a succubus!").
If you have any other ideas, feel free to share them! I'd like to avoid DM tips though. I love reading them but there are hundreds of blogs that already said everything there is to say

As far as really short articles, would a "Encounter Sites" type article interest you?
I am thinking:
- One page max.
- Gives potential hooks.
- Has custom monster stats (but uses improved monsters showcasing DMG's DM toolbox chapter.)
- Has some flavor information.
- Maybe a map that can be printed out for battle mat fans.
- Details the encounter
- Followup and suggested outcomes for vanquishing the threat that is campaign/ setting neutral.
Bring them on! I wanted to finish the two adventures I started before I work on anything else but those are really easy to make and illustrate.