The National Conference of the State Legislatures is an awesome website with a great program called Legislators Back to School Program. Teachers can request a state legislator to visit their classroom. According to the website "NCSL makes available, free of charge, materials for high school, middle/junior high and elementary school students to be used by state legislators visiting the classroom." 

The site also provided several online activities to help students learn how legislatures function. 

http://www.ncsl.org/legislators-staff/legislators/legislators-back-to-school.aspx