National Geographic Kids has a wide variety of games, puzzles, and activities for students of elementary school age. National Geographic Kids has nine games specifically for developing geography skills.
Learning Together offers four activities for learning about the geography of the United States. Learning Together also offers a game about world geography and a game about European geography.
Owl and Mouse Educational Software offers nine, free, interactive maps for students. The maps cover every continent except Antarctica.
Lizard Point gives students 36 interactive maps to study. The maps cover basic world geography as well as specific geography questions for various regions and countries around the world.
Traveler IQ Challenge has 14 interactive geography activities. The activities can be embedded in a blog or website. If it is an option for you, I recommend embedding the activities into your class blog or website to cut down on the number of advertisements that your students see.