[taylodl]

Don't focus on learning development stacks - today's hotness can be tomorrow's old news. Focus instead on doing something. The what is far more important than the how. If you really want to impress prospective colleges and/or employers (be thinking of internships!) then focus on what you want to deliver. What will it do? Hey! Can I run this on my phone?

The best way to figure out what to do is to scratch your own itch. What are your hobbies? I'd do something related to that.