When I did a lot of ASP programming, I used Macromedia Homesite. To my pleasant surprise, when I switched to PHP, I found that Homesite has PHP syntax highlighting. You also get project management utilities (as in organization of documents, not Gantt charts), HTML validation, and if you really need it, there is also a WYSIWYG editor.
Pound for pound, I would say Homesite is the best general editor out there.