KompoZer is an open source, WYSIWYG (What You See Is What You Get), Web / HTML / CSS editor for Windows, Mac and Linux.
Wikipedia article on Kompozer
Home page where you can download this free software
KompoZer 0.7.10 User Guide (original Web page)
KompoZer 0.7.10 User Guide (PDF) 1.5MB
KompoZer 0.7.10 User Guide (MS Word) 1.2MB
KompoZer, built on the NVU architecture, is a good free option that is beginning to approach the functionality of Dreamweaver.
The interface is different than Dreamweaver’s, but it should still feel familiar. Major editing buttons live in a three-tier toolbar at the top of the program that includes a one-click Publishing icon as well as one-click buttons for Image insertion and Table and Form creation. Font tweaks like Size and Style live in toolbars just below for easy HTML editing. A Site Manager, including File tree, is anchored on the left, although it can be collapsed. We didn’t notice any screwups when playing with the WYSIWYG function. Running lean and mean lets KompoZer compete more than adequately with better-known competitors.