Thanks to a tip from a distant relative in the Czech Republic, I became aware of a free offer from Ancestry.com where you can obtain copies of World War I draft registration cards. The free offer runs through the end of February and is available at: http://www.researchguides.net/free.htm.
I found the above draft registration card of my grandfather, Edward Kostal. The card dates from 1917. Interestingly, there were three Edward Kostals available for the draft that year -- two from Nebraska. I wonder if they ever met.