I am also a middle school teacher and have tried to use technology to engage my students. One thing that has worked for me is to use webquests. You can find some really ones at htpp://webquest.org/search/. I've found a website that encourages students to discuss with a science blog. The site for this is http://www.middleschoolscience.org. I haven't used this site yet, but it does look like it would support some student discussion.
I'm curious how this (or something like this) would work out. Let me know if you try it and how it turns out.