iCivics is an online resource for personal study, teaching, and research which helps explain the political process in the USA, through games and activities.

iCivics is free but asks for an optional donation.

I just wanted to second this resource. When I click on the link, it looks like something is going on with the site, but if your kids love history/government, check back later.

I also think some of these games are on BrainPop because my daughter told me she was looking for a BrainPop game when she discovered the site.

It's pretty incredible. I walked in to find my 8 year old playing a game where you matched different rights to their amendments. She had learned which rights were in which amendment just by playing the game. Before this, she didn't even know what the Bill of Rights was.