Several Parenthackers have mentioned this particular trick in the comments of other posts, but I felt it bore repeating given cold-and-yuck season. From Heather:
This is the time of year where germs take up residence at our home and refuse to leave until mid April. During this invasion I become extra vigilant about hand washing. So to make sure we get in our full 20 seconds of "hand friction" we "sing" the theme to Jeopardy. This seems to distract the little ones from the misery they call hand washing and turns it into something fun.