[wernercd]

"Yes, especially doing things that are useful to you."

I'd also expand that to say things that lead you in the direction you want to go.

Game development? Healthcare software? Big business? Small business? Big Data and report writing? Database management?

Once you get past the basics there is a plethora of tools and sites... its important to try and veer towards something that meets those goals.

Euler and Math is good - math crosses all boundaries. But Fibonacci isn't as important to UI or Game programming (depending on the game types, of course)