Mockbin : Mockbin allows you to generate custom endpoints to test, mock, and track HTTP requests & responses between libraries, sockets and APIs.
mail-tester.com : Free online service that allows you to test your emails for Spam, Malformed Content and Mail Server Configuration problems
WebPagetest : Run a free website speed test from multiple locations around the globe using real browsers (IE and Chrome) and at real consumer connection speeds.
TellForm : An opensource alternative to TypeForm that can create stunning mobile-ready forms , surveys and questionnaires.
Yellow Lab Tools : Online test to help speeding up heavy web pages
Increase your form conversions by fixing common usability issues
Enter a URL. FormLinter will find a form on the page and let you know if it can be improved.