Where kids go to smoke during break at school.
Let's go havva ciggie at break, meet you behind the bike sheds.
Bikeshed refers to topics which have never recieved concensus and are likely to generate side-discussions and flames unless all participants are well-read on all the past history. It stems from the idea that big changes (like the building of a power plant) go through quickly, since everyone assumes that someone else has checked it out, while simple changes (like building a bikeshed) often get mired in bureaucracy, since everyone has an opinion on it.
Tom posted a bikeshed topic to the mailing list and awoke to 11,358 messages in his inbox.