I have received a bunch of emails over the last two weeks from people wanting to participate in the search for Mars Polar Lander in HiRISE images, which I am only now responding to. I'm sorry for the delay in my response! Phoenix has kept me just a little bit busy. I've updated the Mars Polar Lander search page with these new additions. Also, the HiRISE team asked me to announce a different way to search the images, using the Zoomify tool, which will be particularly useful for potential searchers operating on computer systems on which they are not permitted to download and install the IAS Viewer -- so this opens it up to many schoolteachers and users whose Internet access is only available at cafes and libraries.
I'll remind searchers that here's a useful backgrounder on how HiRISE images are processed, which may help you as you proceed with your search.
I've gotten several emails from people with possible candidate MPL landers, backshells, parachutes, and other wreckage. I plan to collect these for a little while longer, then examine them, throw out the ones that can't be right because of the scale ("backshells" that are 30 meters in diameter won't make the cut), then send the rest on to the HiRISE team.
Want to participate in the search? Send me an email!