One of our team members, Ross Beyer, put together a way of getting MRO data into the Google Earth tool: http://orrery.us/node/54
I finally got around to trying it out, and it’s very easy to set up following his instructions. It allows you to see the footprints of acquired HiRISE images on a larger context map, and the Google [Planet] interface is really easy to use. Clicking on a red H footprint gives you a short description of the image, and a link right to our image release page, where you can browse or download the image products. CTX footprints are available, too. If I’m understanding this right, these KML files pull all currently released data from the PDS, so whenever we release data, the new stuff is automatically included.
The basemaps aren’t in 3-D (yet – maybe someday?!), so the perspective view isn’t much use, but you can kind of trick yourself into thinking it looks 3-D with the shaded relief maps. You can “fly” over the planet, zooming in & out, which is really fun.
I had trouble trying to get two basemaps visible at once (colorized MOLA elevation over the greyscale MDIM). With just one basemap, though, it works just fine, and it’s very fast (this probably depends a lot on your internet connection).
One really nice thing about the Google interface is when there are two overlapping footprints (which all of our stereo images are), clicking on them expands the choices and allows you to pick one or the other. Other tools I’ve used don’t handle this as nicely, and sometimes it’s impossible to select the “bottom” one.
Nice job, Ross & Google! 
Our image web pages all have this great map feature (click the image to the right for an example). (It’s been there for a while, so you may have noticed it already.) If you scroll down to the bottom, below the Observation Toolbox, you’ll see a mini context map from Google maps for the specific image whose page you’re viewing. It’s so useful to be able to see the HiRISE footprints placed on a broader view of Mars, showing the surrounding geology. Plus, you can pan and zoom around in the map. Way cool.