The Hitchhiker's Guide to Python! : This opinionated guide exists to provide both novice and expert Python developers a best-practice handbook to the installation, configuration, and usa...
regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
Stack Overflow : Stack Overflow is a question and answer site for professional and enthusiast programmers.
The Big List of Naughty Strings : The Big List of Naughty Strings is a list of strings which have a high probability of causing issues when used as user-input data.
Collection of thinking tools and frameworks to help you solve problems, make decisions and understand systems.