Google Engineering Practices Documentation
"Google has many generalized engineering practices that cover all languages and all projects. These documents represent our collective experience of various best practices that we have developed over time." Unfortunately it currently contains only "Google's Code Review Guidelines".
Awesome Software and Architectural Design Patterns
"A curated list of software and architecture related design patterns."
Tools of the trade
"Library that handles all the email validation strategies: regex, common typos, disposable email blacklists, MX record lookup, and SMTP to check the inbox exists." (from Weekend Reading)