I have approximately 1 hour of free time scheduled in during my very busy summer, and I'm wondering what sort of productive/programming/money-making thing(s) I should spend my time on? For instance, is that enough time to say, develop an app fully in during the summer?
Borrowing from Richard Hamming via Paul Graham--<p>* What are the most important problems in your field?<p>* Are you working on one of them?<p>* Why not?
An hour a day all summer is enough time to develop an app. However I am not sure this qualifies as "productive" or "money-making!"<p>In seriousness, it depends a lot on where you are in your life, and what your goals are. I would give very different advice to a student on summer break than I would to someone in the working world and with a family.
Learn something new. Spend one hour a day messing with code. Or watching up to 2 or 3 video tutorials. Or reading one hour of a programming book a day.