Tools

Files

FileFormat.info

Fitnesse

DbFit: Test-driven database development
FitNesse Fixture Gallery
Test Driven .NET Development with FitNesse

Formatter

Free Formatter (Formatter & Validator)

Git

Git Command Explorer
Oh Shit, Git!?!

JavaScript

JS Bin - Collaborative JavaScript Debugging
JSFiddle - Code Playground
JSONPath Online Evaluator

JSON

JSON Formatter & Validator
JSON Schema Generator
JSON Minify

Mocking

Regular Expressions

RegExer
Regular expressions 101 (PCRE (PHP), ECMAScript (JavaScript), Python & Golang)
Rubular (Ruby)

SQL

Instant SQL Formatter
SQLFlow

Test data generation

BestRandoms
Mockaroo

Wget