This site gives students the opportunity to watch campaign ads from presidential elections from 1952 to 2012. It's a cool way to teach about propaganda and political advertising. The site is www.livingroomcandidate.org
I'm trying this again . . . Docs Teach is digital "warehouse" of primary source documents that include interactive activities, such as evaluating evidence to make a case for a particular argument. This is very useful resource for a social studies class.
Edmodo is a cool tool to use with the students to increase engagement outside the classroom. It looks a lot like Facebook so the students are familiar with how to use it. I use to have off site discussions and to administer quizzes and I love it!! PGCPS pays for a subscription, but I am not sure if that is the case for other school systems.