Dave Fletcher reports that the four of the five top eGovernment Web sites in the Best of the Web contest run on Linux, Apache, and Resin. I'm not sure Resin's open source, but the point is well taken.
Dave also points to the UK's eGovernment office's open source policy (PDF). How many other government's have explicit open source policies? I don't know, but would be interested in compiling a list. If you've got any pointers, send me a note or add a comment below.