NASA has an excellent interactive timeline tracing the history of astronomy and space exploration from the Greek philosophers through the current day.
Planet Quest is actually three timelines combined into one. The three timelines cover technology, discovery, and culture as it relates to astronomy and space exploration. Each element on the timeline is narrated. Users can select individual elements on the timeline or choose autoplay to hear the narration of each item in sequence.
This is a neat website that lets students track missions as they are happening with the satellites that are collecting information about the Earth from space. Students can learn about the earth by choosing a mission to follow, zoom in and out of the globe, view satellite paths, view city and location labels on the map, replace the sun with an "artificial light" and see the view from Earth's surface. As students click on the satellite, they will be able to view and discover more information about the mission. Students can choose to view the 3D Earth in real-time or speed up/slow down the Earth with a time control.