A few weeks ago the FamilySearch blog posted about Source Tracker, a web app that hooks into FamilySearch and shows you which U.S. censuses your ancestors should have been in, and (more importantly) which ones have already been sourced. For example:

Yes, please. It’s brilliant. And it makes it really, really easy to see where the holes are — in mine, for example, you can see that I need to find Mary Louise Chambers in the 1880, 1930, and 1940 censuses. Clicking the magnifying glass takes you to a search for that person in that census. I’ve spent a fair amount of time these past couple weeks going through and hunting people down in the censuses (and I still have a lot to do, as you can see).