Here's a great resource for older kids for teaching citizenship, American Gov't and such:
Youth Leadership Initiative (http://www.youthleadership.net/index.jsp)
It's completely free and they have mock elections, free lesson plans, free cd (although it's currently backordered till March) and E-Congress. Seamus is signed up for the E-Congress and he's really enjoying it.
If you're interested in the E-Congress, hurry up and sign up soon, as the deadline for teachers to sign students up for the E-Congress is 2/24.