Social bees of several genera such as Trigona and Melipona are commonly known as stingless bees. They are mostly tropical and can be found in much of Southeast Asia, Australia and tropical South America.
Nests of stingless bees are usually built inside a crevice. There is often a structure made of wax or secretions from the bees surrounding the entrance hole. These bees, like honeybees, do make honey, and they have much in common with the honeybees. Although they are considered less advanced, interesting observations of their behaviour have been made. Some info about Australian stingless bees can be found here.
Stingless bees do in fact have stings. It is just that their stings are too small and weak to penetrate human skin. However, some species ferociously defend their colonies by biting and even spraying certain chemicals which cause a painful burning sensation. However, they are not particularly defensive if the nest is left alone, and do not pose a threat in most cases. Colonies can sometimes get very large. They swarm in large numbers at certain times of the year, congregating on wooden posts and branches before starting new nests.
The nest below belongs to what is probably Singapore's largest stingless bee, a common insect about 3mm to 5mm in length and with attractively-patterned wings. The nest photos copyright and courtesy of E-Trails (Singapore).
Photo below copyright and courtesy of Tan Siong-Kiat. This is one of the smallest species in Singapore, and is quite commonly seen at flowers.
Another shot of a small stingless bee from Singapore.
Above: A stingless bee nest in an unlikely location; inside a lamppost! The bee here appears to be mending the entrance.
Below: Note the shape of the entrance extension. These photos taken from Singapore in 2005.