Notepad is for lusers. Sorry, I like not having to count out the line numbers in my code.
Dreamweaver is the best at the moment. Download the demo from Macromedia. Not only does it have the WYSIWYG editor, the text editor portion is pretty good. Line numbers, code reference, code completion, tabbed editing. There are modules for different languages (i.e. ASP, PHP, etc.) and I think you can download others from the website.
If you want to go cheap, get Textpad. Tabbed file editing and line numbers.