The High Resolution Imaging Science Experiment at the University of Arizona is hosting some gigantic images snapped (or rather scanned) by the Mars Reconnaissance Orbiter (MRO). The full version of the image shown below is 31,850 x 77,994 pixels! Each pixel represents 30 cm on the Martian surface.
It wasn't until Photoshop CS (8.0) that the program could even accept images bigger than 32,767 on a side, and few available file format modules can import such images, but j2k 2.01 can. Granted, doing so can take quite a while between the decompression process and all the virtual memory swapping Photoshop needs to do to.
A more efficient way to browse their JPEG 2000 images is by clicking on a link that brings up the Java-based IAS Viewer, which dynamically loads just the part of the image you're viewing at just the resolution you need, taking advantage of one of the key features in JPEG 2000. They also have a sweet Flash-based app to do the same. This reminds me of a personal feature wish for j2k to allow the user to reduce resolution when importing big files into Photoshop.
The idea behind the project is that members of the public will scan the images for features and report the interesting bits back to scientists.