The Advanced Camera for Surveys (ACS) is no longer working. This same instrument has had troubles before and had been operating on a set of backup electronics, but it appears that those too have failed.
Given the enormous success with the Mars rovers, lasting many times longer than initially thought, it can be difficult to remember just how harsh the environment of space really is to electronics. The ACS had an expected lifetime of five years and was only a couple months shy of that expectation.
You can find lots of images from the ACS at its website.