As beobab said, code, debug, feedback, rinse and repeat
Other resources that were helpful for me as well
Books:
- SICP (http://mitpress.mit.edu/sicp/full-text/book/book.html)
- The Pragmatic Programmer: From Journeyman to Master
Courses:
- Almost all udacity CS classes
- SaaS courses at edx.org
- Scala course and most CS courses in coursera
Open source:
- browse most popular OS projects on GH, and try to contribute
- create your own open source project, and get feedback / pull requests
Q&A sites:
- Stackoverflow
- http://codereview.stackexchange.com
and of course most coding related articles here on HN
edit: SICP has an online course at MIT OCW:
http://ocw.mit.edu/courses/electrical-engineering-and-comput...
it might cover a lot of things you know, but I think it's a must have for every developer out there.