There are several of those types of applications around, with varying features. You can find a really good list of such things, with “live demos” so you can see them in action, at http://opensourcecms.com.
You might look at WebsiteBaker, as just one example (I have a couple of clients that are very happy with it),
Another that is “dead simple”, but actually does a very nice job for being “easy to use” is CMSimple, which also happens to have a great number of really nice templates (free and inexpensive) available.
finally, you might consider that WordPress, while primarily designed as blogging software, has actually evolved into a nice CMS for “non-blog” style content (with it’s recently developed “Pages” features) and many are using it in exactly the way that you describe.
It already has all the access control stuff, and reasonable editor, and file and image uploading built-in. With it being a “one click” on DreamHost, it may well be the easiest way to do what you want - just don’t use it as a blog. Here is a “very simple” example of WordPress used simply as a “site builder” - http://www.devraweb.com. In addition to it’s ease of use, WordPress has an amazing number of good-looking “free” themes available too!