Did anyone know that nitrous oxide was being sold in nightclubs and bars in the UK? How come nobody told me? Well, the good times may be coming to an end in the face of a new "purge" to get the gas out of people's hands. From the Times Online:
Nightclubs, bars and festivals that sell nitrous oxide face prosecution as part of a purge on the recreational use of the chemical.
Drug regulators said yesterday that anyone supplying the compound, commonly known as laughing gas, for recreational inhalation was complicit in an activity that carried serious health risks and would be prosecuted.
This is a fairly decent article on the effects and dangers of nitrous oxide, including a short history of the substance at the bottom of the page.