Notepad++ is a powerful editor that replaces and extends the functionality of notepad and provides quite a lot of useful features.
One particular thing it excels at is all of the syntax highlighting and folding (minimizing and expanding segments of code) it supports. C/C++, Ruby, Python, PHP, XML, Matlab and Perl are few worth mentioning. Additionally, you can create your own Syntax highlighting if a language you want to use is not supported.
Notepad++ also features a tabbed interface for easy navigation and tons of flexibility.
Completely Free and Available Here:
.:: NOTEPAD++ ::.