I've been thinking about this - all these people showed up in Florida for the 2000 general elections and found out they'd been removed from the voter rolls before the election (see
http://www.gregpalast.com/columns.cfm?subject_id=1&subject_name=Theft%20of%20Presidency if you want to know more about this). I don't know much about if they still do the purge or whatever, but it seems like one of the only ways to prevent this is to call up and check every now and then to make sure you're still on. Who for sure would you call about this? The secretary of state's office? Some other election authority? Does it vary by state? And what states are out there that remove felons from the voting records (which have a risk of removing more than just that)? If we pool our resources, we might be able to collect enough information to make sure we and our Democratic friends don't end up stranded on election day.