WinAVR is well known AVR-GCC toolset for Windows users. In general these are command line tools that might be unattractive for many microcontroller developers. Using graphical interfaces makes things much easier. Actually there is a nice IDE in WinAVR package called Programmers Notepad. But it lacks some nice features like syntax highlighting and other options like custom themes. Of course you can always use AVRStudio or Eclipse as IDE as alternatives. Vassilis has been using Notepad++ for some time and decided to set up it to work with AVR-GCC like it were in Programmers Notepad but with all Notepad++ features.
He was able to integrate make commands with help of NppExec plugin. Vassilis put all commands in selectable macro menu so you could compile and program with single mouse click. So if you have worked with Notepad++ before, hawing it working with WinAVR is a great addition to portfolio.