I speak standing on a hill if my own dead projects. Just remember personal projects are supposed to be fun and educational, maybe with a little resume padding for good measure. Scratch that itch you can’t get to at work. It’s great when other people enjoy them, but as soon as they become a commitment, they start feeling like work. To me, at least.

That’s why I think games or little tools are great. They small enough so you can throw them out and start over. People won’t get (too) mad if you stop maintaining them (if you open source them) because it’s easy for someone else to take over.

I don’t have a concrete idea for you, but I suggest starting with something really simple. I think simple games are a good place to start. Or create a front-end for some command line tool to make it easier on beginners. That way you can focus on the UI development you’re interested in without getting bogged down in the rest of it.