If you don't mind typing a bit of markup, I suggest you use a preprocessor like Markdown. Write in "plain text" (Markdown looks mostly like e-mails), convert it to html, then paste the result through the "HTML source" button.

If you don't mind a bit of markup, that may suit you.

Now for a plain text editor that doesn't suck, I don't know what to promote. I personally love Emacs, if only because you can install a Markdown mode that highlight your headers and slants your emphasises, but my love is partly due to my heavily customized key-bindings (the default ones are often clumsy). Overall, use anything but Windows' Notepad.