The cool cats over at JPL have assembled and posted some really nice color mosaics from both of the Mars Exploration Rovers. I especially love this one (full resolution version here, which shows the impact site for Opportunity's heat shield.
Opportunity spent quite a while investigating the heat shield impact site. As you can see from this very cool vertical projection assembled from Navcam pictures, that gives us a great "overhead" view, the rover covered all of the ground around this site. The polar projection is also quite informative.
There's also a great Spirit mosaic from several months ago. This image covers an area that Spirit's been traversing in Columbia hills. Check out the quicktime animation for a nice 360 degree panorama.
The rovers are still in good health and continue to make tracks on their respective sides of the planet.