Fox News has an article on the letter sent to Walter Reed. The article includes a list of other servicemen there to write to.

Capt. James Ollinger
Sgt. Zavian Simspon
Specialist Brian Radke
Specialist Jason Braase
Sgt. David Nevins
Sgt. Jose Ramos
Cpl. Todd Bishop
Sgt. Ryan Donnelly
Sgt. Eva Diane Cochran

They should all be written with their name and then

C/O Walter Reed Army Medical Center
6900 Georgia Avenue NW
Washington, DC 20307-5001

Yahoo. I have a bunch of cards from the women at church that I want to mail. And my college kids are writing letters, too.