Via MetaFilter: Children high on sewage. This relates to a rather old news item that asserts the existence of jenkem (aka jekem) - a form of hallucinogenic drug used by street children in Zambia created by fermenting sewage in a plastic bottle.
Despite its repetition by major sources such as UNICEF and Associated Press (a common factor is an NGO called Fountain of Hope as quoted source) I can't decide if this is urban myth or not. On the one hand, fermenting sewage is well-known to produce mainly carbon dioxide and methane. The creation of an alleged strong hallucinogen requires some novel chemistry, and it seems strange that there aren't accounts of this effect from sewer, sewage farm and biogas plant workers. On the other, the smell of faeces is due to the presence of skatole and indole, whose bicyclic structure is highly amenable to substitution and is the basis of a number of classic hallucinogens such as psilocybin and 5-MeO-DMT - so some organic reaction is not entirely implausible. Nevetheless, the story does fall into the class of those not critically analysed because it arises in circumstances where few would want to investigate.
Indoles are interesting compounds: in high concentrations they smell of dung; at low concentrations they smell of violets. One notable occurrence is in boar meat, where they contribute along with androstenone to an unpleasant smell and taste on cooking, "boar taint". Measures (apart from the traditional castration) to reduce/remove this are an ongoing topic of research in agricultural science. See, for instance, Genetics of Boar Taint: Implications for the Future Use of Intact Males. Other pork products such as offal contain indoles that contribute to a gamey flavour: one of the early food pairings predicted by molecular gastronomy was that of pork liver and jasmine, which both contain indole.