I'm doing a 30 day squat challenge, which I guess is all over Pinterest, but I first heard about it through Nicole (who is also the brains behind Monthly Measures). So far, so good, but it's only day 6.
I also recently downloaded the Daily Workouts app to my iPhone. There is a free version, which I started with, but then I sprung for the $3.99 to get the full version. You can focus on an area or do cardio or a full workout and you specify for how long you want to work out. Then a video starts which shows you the exercise and then tells you when to switch to the next one. There are also in-app add-ons you can purchase, like kettle bell workouts or stretches or Pilates (I haven't done any of those yet).
I really want to step it up a notch this next month. We leave for Europe in 32 days!