I made a post the other day about worms without mentioning Stuxnet, which may have hosed the nuclear processing going on in Iran. Current theory is that the worm was a joint US/Israel venture, but there are other theories out there.
There have certainly been other instances of computer worms endangering infrastructure both online and offline:
In 2003, the SQL Slammer worm caused network problems in an Ohio nuclear plant, although there was an analog backup for much of the functionality and furthermore the plant was offline.
- February (5)