Use Your Coffee Cup as a Basic Barometer

Instructables user stickmop shares a trick to tell basic barometric pressure using a hot cup of coffee, tea, or cocoa; when you pour the coffee into the cup watch the bubbles. If they move to the edge of the cup quickly you can expect clear skies for the next 12 hours, if they hang out in the center expect rain in the next 12 hours, and if the bubbles move slowly to the edge you may get a bit of weather, but it will clear soon.

This trick came from a long ago issue of Backpacker Magazine. If you're out camping without an internet connection it may come in handy someday.