I guess weather apps are part of what we would qualify part of our daily routine, personally I related myself to Google Apps. But they are a numerous amount of applications out there that shares a "fun" factor to the mix.
A great to exercise our skills and to evolve into better designers is daily practice. All the great names out there have practiced their skills and became people to look after. Hezy, a design group based in New York, started a 100 days challenge called "Daily UI Elements" in which they'll challenge you to design a certain piece of interface.
Here are some examples of what they've done so far. You should really follow this project and make your own pieces as they challenge you daily. I hope you enjoy this! Keep evolving! Cheers. ;)