Pretty much anything. Even if you're just working your way through some tutorial on $SOME_TOPIC, put the code in a repo. Later, if you're applying / interviewing somewhere, it will still be of interest, even if it isn't some standalone, super-fancy, gee-whiz, flashy $WHATEVER.
If I were interviewing somebody who had only tutorial or exploratory code up, I'd just use it to seed the conversation. "I see you used a while loop here... is there a way you could do the same thing with a for loop instead?" or "You did this tutorial a year ago, based on what you've learned since then, how would you rewrite this bit?" and things of that nature.
Over time, as you start writing bigger and more functional apps or systems, you'll obviate the need for that stuff, but use what you've got.