Nvu is an Open Source (free!) web editing package to rival Dreamweaver or Frontpage.
It’s really easy to use, enabling you to work directly in code, or in a WYSIWYG environment, and it generates standards-compliant code. It’s based on the Mozilla Gecko rendering engine, and is currently at version 1.00PR, so there still bugs around.
Available for Linux, Windows and Mac OSX from the official download page