Loop Habit Tracker
Free and open source app to track your habits
I'm a fan of little, simple and useful apps, and if they're free, much better. Few months ago I was looking for something to keep track of my reading, writing and exercise routines. I needed something simple and easy to use, wasn't looking for anything fancy. That's how I discovered Loop Habit Tracker, and after one year I keep using it daily.
You can set the periodicity for your activities, set reminders, personalize the colors, have access to your stats (even export them to CSV), and easily mark your tasks as completed with the widgets. It might sound stupid, but if you lack of consistency like me, this app can help you complete the tasks you want to do regularly. Unfortunately, it's only available for Android.