Ancestry.com is offering a free chance to look up military records from now until June 6th.
http://www.ancestry.com/
When you get to the site, just click the militaristic-looking graphic on the right.
It's pretty neat. Just plug-in the name of your ancestor and info of varying degrees pops up (ideally). Note that there may be entries on your ancestor or friend on more than one site. Pretty rudimentary, but fascinating just the same.