Ask HN: What's the cleverest or most indispensable recipe you've seen for IFTTT?

For IFTTT, Microsoft Flow, Zapier, etc: what are the cleverest or most useful recipes you've seen? I ask because a lot of the examples seem to lack vision. It's fun to get an email when you upload a photo, or retweet a facebook post. But what, if anything, has been done with these services that is outright indispensable? Have they ever saved your butt or made you money?