EasyIDE is an IDE for Mathematica, written in Mathematica.
EasyIDE is in beta. Please make sure to commit your work frequently as I cannot yet be entirely certain that there will be no nasty state-losing bugs. I have written 90% of EasyIDE using the system itself, but I can only attest for my personal experience as its creator.
The easiest way to install EasyIDE is from the Paclet Server
To use EasyIDE just create a new notebook and go to Format > Stylesheet > EasyIDE > LightMode . The notebook will ask you for a location to use as the root directory. This can be changed via the Project menu at any time.