ConTEXT

ConTEXT is a powerful freeware programmers text editor, and is much, much better for writing your mel script in than either Notepad or Maya's script editor. It has a powerful search engine, shows line numbers, has programmer-style tab indents, and with the highlighter file I have written for MEL it will even colorize your mel scripts for you.

ConTEXT Files
Official Website: http://fixedsys.com/context/

Download from here (may be a version behind): http://www.alexhogan.com/files/conText/ConTEXTsetup.exe
(Right click the link and select "Save As" to save)

Download the MEL highlighter file: http://www.alexhogan.com/files/conText/mel.chl
(Right click the link and select "Save As" to save)

ConText Instructions

-Download and Install ConText to c:\program files\conText\
-Right click and download the mel.chl highlighter file to c:\program files\conText\highlighters\
    -Set your file mask to *.* in the save window so it doesn't save as "mel.chl.txt"
-Run conText and configure it how you like by going to Options -> Environment Options on the menu