WhatWeb

Often as a developer you feel like understanding the technologies used for building a particular website. Though there are many already available solutions out there, WhatWeb is a FREE and OPEN-SOURCE piece of code that helps you scan a website for it's underlying technologies.

You can know more about the project over here- https://www.morningstarsecurity.com/research/whatweb or download the code from GitHub- https://github.com/urbanadventurer/WhatWeb