- drupal.org
- Drupal Planet - latest blog posts from a wide variety of people working with Drupal
- API documentation
- general developer documentation
- Examples for Developers - small example modules that demonstrate how to work with various APIs
- Writing secure code
- Security advisories
- Coding standards
- Coder - checks Drupal code against coding standards and other best practices
- Drupal Groups - various Drupal-related special interest groups, though some of the groups are ghost towns because the site hans't been updated in quite a while and the UI is kludgy
- Drupal Answers - a StackExchange Q&A site (great for asking the community one-off questions that have a clearly defined answer)
- simplytest.me - short-lived demo sites (great for quick testing of modules, themes, and distributions; not all distributions seem to work smoothly here though)
- Pantheon - platform as a service hosting (offers free developer accounts; great for quickly testing fresh installs of distributions, modules, etc.)
- Pro Drupal Development - sadly, the Drupal 7 version of the book isn't quite as comprehensive as earlier versions, but it's still a good starting place for learning Drupal development best practices
- Definitive Guide to Drupal 7 - written by many authors, so a bit disjointed and redundant at times, but does provide a lot of information
- Drupal resources on O'Reilly Safari - lots of Drupal resources, if you happen to have a Safari subscription
- Drupal books from Packt publishing - Packt publishes a lot of Drupal books, but the quality can vary quite a bit, most (all?) are also hosted on O'Reilly Safarai (above)
- Drupal.tv - LOTS of conference videos across a wide variety of Drupal topics
- Drupal Association on YouTube - lots of Drupalcon conference videos
- Drupalize.Me - lots of tutorial videos on a variety of topics (design, theming, development, site building, etc.)
- DrupalCon Austin 2014: Securing Your Drupal Site: Advice for Site Builders and Coders
- DrupalCon Austin 2014: Semantic Site Architecture
- DrupalCon Amsterdam 2014: Panels, Display Suite, and Context - oh my! What to use when, why, and how
- DrupalCon Amsterdam 2014: Future-Proof your Drupal 7 site
- http://drupaleasy.com/podcast
- https://modulesunraveled.com/podcast
- http://www.acquia.com/resources/podcasts
- https://www.lullabot.com/blog/podcasts
- http://www.drupical.com/
- http://www.meetup.com/ (Austin has multiple groups and multiple meetups)
- Implementing a Strong Code-Review Culture (presentation video)
- Doing Daily Battle with the Curse of Knowledge (blog post)
- How I Judge the Quality of Documentation in 30 Seconds (blog post)