Vietnam Backpackers Hostel: one of a chain of party hostels through Vietnam. Had a really high rooftop bar with great views and deals on food and drink, but the party side of it didn't suit us having just arrived and being so jetlagged.
Cu Chi Tunnels: a day tour of the Vietcong tunnels north of HCM organised through STA Travel. We got a good deal and it was a private tour for only five people, with a very friendly young guide who took us around the area and told us about how young people perceive the conflict and what their lives are like now.
War Remnants Museum: quite a moving museum that isn't censored at all, and shows the horrors of the war with the USA. Very interesting throughout, with plenty of great exhibits and real equipment left over from the war.
Ben Thanh Market: large market near the backpacker area, which will often overcharge tourists for even the basics. I was asked for 60k VND for a Coke when it should normally be 10-15k.
Street food is amazing in Vietnam, so it's always easy to go up to a vendor and ask for a Banh Mi (baguette style sandwich thing with meats, cheeses, eggs etc). The backpacker street also had a few really good restaurants and bars, but they are more expensive than other areas because it is specifically aimed at tourists. There are also coffee shops all over the place, which serve delicious Vietnamese iced coffee, and often give you iced tea for free too. I drank this coffee most days on the trip.