One of the most memorable days we had while travelling in Vietnam was to do a Hanoi Kids tour. Being the sceptical, cynical bloke that I am when my wife said there is a tour where university students take you around Hanoi for free. My response was whats the catch. There was none. We met a lovely woman who tailored the day we wanted and took us around explaining the history of different spots we visited. She also took us to a lovely spot for lunch. We did pay for her lunch, the taxi rides and gave a donation at the end of the tour to the organisation that runs Hanoi Kids, but you are under no obligation to do this.
If you’re in Hanoi then contact Hanoi Kids. There is a reason that they consistently get five-star reviews on trip advisor. Check out my review of Hanoi Kids and others of our time in Vietnam at kiwiinbrighton or specifically for Hanoi Kids at http://www.tripadvisor.co.uk/ShowUserReviews-g293924-d1752779-r269631182-HanoiKids_Tour-Hanoi.html