What is a meme?

According to Richard Dawkins, who introduced the topic in his 1976 book The Selfish Gene, a meme is "the cultural equivalent of genes; ideas--such as fashion, religion, or other cultural phenomena--took on a life of their own within society and, along with genes, affected the progress of human evolution." The science of memetics is fascinating - but controversial. For an engaging introduction designed for the layman, try Virus of the Mind: The New Science of the Meme by Richard Brodie. Well worth a look!