I found a really great history site this  morning, it has a Visual History of the Last 100 Years.  I got it from the blog Free Technology for Teachers, and I admit I get some of my best resources from this blog.  I loved this, it quickly explains the events with graphics to support the text.  There are timelines, and infographics.  Teens get so bored with dry explanations, this seems a nice way to bring a little more interest into this topicl