Fckeditor

This HTML text editor brings to the web many of the powerful functionalities of known desktop editors like Word. It's really lightweight and doesn't require any kind of installation in the client computer.
As it is Open Source, you are allowed to use it for free wherever you want.

http://www.clubic.com/photo/00077484.jpg

The editor provides many HTML editing feature like:
XHTML support
Font formatting: type, size, color, style, bold, italic, etc
Text formatting: alignment, indentation, bullets list, etc
Cut, Paste and Past as Plain Text, Undo and Redo
Paste from Word cleanup with auto detection
Link creation
Image insertion, with upload and server browsing support
Table creation and editing (add, delete rows, etc)
Table cells editing (size, colors, etc)
Right click context menus support
Complete toolbar customization
CSS support for a better integration in your web site
Multi-language support with automatic client language detection.
Lightweight and fast
Compatible with Internet Explorer 5+
Automatic browser detection and customization
Integration with ASP, ASP.NET, ColdFusion, PHP, Javascript and IE Behaviours
Image and file links upload and server repository browser.
For web developer it is easy to install and customize
For web users its simply easy to use!

http://www.fredck.com/fckeditor/