I'm guessing you've already been by now, but the Hao Lo (Hanoi Hilton) prison is interesting. We walked a lot in Hanoi and Saigon(Ho Chi Minh City)...it gives you a real feel. Renaissance Riverside in Saigon is a great place to stay and walking distance to major market, which is a real experience. Hilton in Hanoi (no Marriotts there) is also very nice. From Renaissance you can also take a hydrofoil boat ride to Vung Tau which has nice beaches and is where U.S. servicemen had in country R&R during the war.