I would stick with a text editor and avoid fancy
IDE's for the learning process. Most anything that is not notepad will do. I would look for something with syntax highlighting and perhaps auto-indention. These are sometimes called Source Code Editors or Programing text editors. Try some and see what you like! I prefer Geany at the moment. Here is a list of common editors, though there are many more:
Crimson Editor (Windows)
Emacs (Cross-platform, including Unix, Linux, Mac OS X, Windows)
Geany (Linux, Windows)
jEdit (Windows, Linux, Mac OS X)
Kate/KDevelop (KDE)
NEdit (Linux, Unix, Mac OS X)
Notepad++ (Windows)
Programmer's Notepad text/source code editor (Windows)
PSPad (Windows)
SciTE (Windows, Linux)
TextMate (Mac OS X)
TextPad (Windows)
UltraEdit (Windows)
vi/Vim (Cross-platform, including Unix, Linux, Mac OS X, Windows)
*EDIT* I forgot to mention that I am also in the process of learning. I am in no way an authority, but this has worked well for me so far.