A meme (, rhyming with “cream” ) is a postulated unit of cultural ideas, symbols or practices, which can be transmitted from one mind to another …
The British scientist Richard Dawkins introduced the word “meme” in The Selfish Gene (1976) as a basis for discussion of evolutionary principles in explaining the spread of ideas and cultural phenomena. Examples of memes given in the book included melodies, catch-phrases, beliefs (notably religious beliefs), clothing fashion, and the technology of building arches.
There is even a site with Daily Memes (suggestions for bloggers).
Know Your Meme: Documenting Internet phenomena: viral videos, image macros, catchphrases, web celebs and more.