I've tried a lot (including PHPDesigner2006, WeBuilder 2006 / Rapid PHP, Zend IDE, Dreamweaver, Notepad, Notepad2, Notepad++, and others) to really see what I like best. Ultimately, I ended up stopping on a $20 program called EditPlus. It handles all file formats, and the user base is large enough to allow for syntax highlighting for almost any file / language.
EditPlus is what I use on a daily basis to code my pages. Easy to configure, small, and light. But that's just my suggestion.
Also, might I suggest you peruse this thread 🙂 You may find more editors than you can shake a stick at there!!