Weebly
![Picture](/uploads/7/6/3/9/7639044/2220944.jpg)
Weebly allows you to create ad-free professional-looking websites in just a matter of minutes: this is one of the best web-design tools around, extremely easy to learn and to use. No need to know HTML: just use one of Weebly's template (which you can customize at will), add pages, text, photos, videos, contact forms, documents, etc. The site you are looking now is created with Weebly. You can create a class website such as the one I'm using for my Geography class which you can share with your students. Students can also create their own sites to organize their notes, etc, as a "virtual binder".
Google Sites
![Picture](/uploads/7/6/3/9/7639044/766511.jpg)
Google Sites simplifies web-design, although the result is not as professional-looking as sites created with Weebly. But it's still a great (free) design tool nevertheless.
Wikispaces
![Picture](/uploads/7/6/3/9/7639044/3368341.png)
This spin-off from Wikipedia allows you to create "wikis" which are essentially very basic (free) websites. It's very easy to learn and easy to use and the result looks very similar to sites created with Google Sites.