There are numerous such editors available (like the ones used by WordPress and Joomla!), but they need to be integrated with your website in some way in order to be useful. TinyMCE, fckEditor, Xnha, the older htmlarea, etc. provide some of that functionality, but they can be difficult for inexperienced users to implement.
There are services that let you edit a page online (using these, or similar) technologies, and I suppose you could use them to build a page and then save it to your computer for subsequent upload to your site (check out Google Pages).
Other web hosts sometimes offer "website builder" scripts for doing similar things, but DreamHost does not. I'm curious as to why you don't just use Netscape Composer (or better yet, NVU!) for "building" your pages "offline" for subsequent upload to Dreamhost? That really is the way to go, IMHO.
I don't know if that information is at all helpful, but it's really the only help I can provide without knowing more about what you are trying to do and/or your capabilities with this kind of stuff.