Below are panning stereo pairs of the "blueberries" in the soil at Opportunity's site. You can read about them on NASA's page, which links to a medium-sized anaglyph. The pairs below were split out of the full-sized anaglyph that NASA also released.
Use the left two images to view with the cross-eyed method, or the right two
images to view with the parallel-eyed method. The arrows below the images let
you pan the large images around in the viewports. The buttons above the images
let you adjust the viewport width to suit your eyes and your monitor.
Images courtesy NASA/JPL-Caltech.