As someone with a strong math and science background but who came late to the code game, who has never been able to align the stars for a CS degree or work in programming, Project Euler has been crucial. I can wrap my head around pretty much any math you want to throw at me, but Project Euler gives me the opportunity to know I'm tackling a language-skill-appropriate challenge and immense satisfaction once it's figured out.

That and HN meetups.