I'm glad that someone mentioned The Ballad of Penny Evans. Either that or Feel like I'm fixin' to Die Rag would be my choice. There were a lot of great anti-war songs from that era, but these two specificallly mention Vietnam.

For psychedelic tunes, I'm thinking of pieces that "Pushed the Bubble". Jimi Hendrix's Third Stone from the Sun from his first ablum comes to mind. So does Streetmasse, the much more obscure contribution of Spencer Dryden to Jefferson Airplane's After Bathing at Baxters.