Awesome post!
For those looking to develop in data intensive environments, you will most likely need some SQL knowledge.
This is a great place to start:
sqlzoo.net
This site is where I learned the basics. I now use this site to teach an intro SQL class to my department at a Fortune 50 company.
Meetups and user groups are good; Some subreddits are helpful, some will send you to SO. IRC channels and mailing lists/google groups are helpful to various degrees
3. First Job
github portfolio is key, along with good writing (both tech bullet points and clear communications) on Stackoverflow, mailing lists or blog.
sqlzoo.net
This site is where I learned the basics. I now use this site to teach an intro SQL class to my department at a Fortune 50 company.