Those of you movie buffs may have seen depictions of cyclos on the silver screen. Of the three well-known overseas Vietnamese movies made in the last several years, two of them, Cyclo and Three Seasons, have protagonists who are cyclo drivers. They are indeed a Vietnamese institution, and no matter what you decide to do in Saigon, getting onto a cyclo is a must experience once, though many people who visited have preferred this as their exclusive method of transportation.
The cyclo is a three-wheeled rickshaw, which are usually pedaled by thin, battered old men. The cyclo differs from the Chinese rickshaw in that it is pedaled, not pulled, and because the seat is attached to the front of the pedaling mechanism, you have a great view. You can find cyclos anywhere in the city, so just flag down one. Cyclo drivers are usually excellent city guides--they know every inch of Saigon, so actually hiring one for the whole day is a great way to see Saigon.
Riding in a cyclo is usually a bargain, as the cyclo drivers have to work very hard to earn a little money. So if you don't do this anywhere else in Saigon, do evoke your humanity when riding a cyclo. By this I mean don't try to cheat a cyclo driver by an additional US$.10--it does not mean anything to you but plenty to them. And do try to sit by yourself if at all possible. I have seen western tourists riding two-at-a time on a cyclo, and the seat is just totally weighed down. Do imagine how it is for those poor peddlers. Vietnamese can usually get by with it because of their size. So just look at yourself before you decide to pile into a cyclo.