I've recently started using Twitter, mostly just to consume; I've only posted a few tweets (and somehow the link got dropped from my latest tweet).
Anyway, one that I'm following is 'History in Pictures' (@HistoryInPics), which regularly shows neat stuff. One thing that I know I didn't appreciate when I was younger, was how a suspension bridge works. But this picture showing the bridge in progress really makes it clear in a way that no textual description can.
Like I said, neat stuff.