http://www.educationworld.com/a_less...ateideas.shtml
I also like Mrs. Waffenschmidt, from the same website. However, it is worldwide landmarks. US landmarks would be fun to learn about. You could create a powerpoint with their pictures. Students could try to name the state they are located within and then find the state on a US map. They will have seen these places in movies so they should have some prior knowledge about them.
I would get a large scale puzzle of the US for them to do on rainy days at recess. Time them and see if they can beat their time from before. Or maybe get two puzzles so they can race and see who completes it first.
There is an online game called Know your states. I would have them practice this as well.
http://jimspages.com/States.htm
Buy several US maps. I would get enough for students to work in pairs on the floor. Create a list of questions that are specific to the map's design and will also help them to learn the states. It is a race to see which team can find the answer first. Then they should help you show the others how to locate the answer. this will add a cooperative aspect to the lesson.
Have each student research a state and create a brochure. Then share the brochure with their classmates to learn more about each state.