Barring anything unforeseen, the next Landsat satellite should liftoff in early 2013. NASA has an interesting Twitter page of announcements and opportunities for the wide range of its users. In addition, a recent full free issue of Remote Sensing and the Environment contained lots of articles about the exciting past, present and, future of the Landsat program. A cool brochure is also available. Be sure to check it out! When it comes to free data, Landsat has to come to your mind!
Comparison of Landsat Satellites -- What's Ahead... (Click on the Image to Enlarge)