Snowclones are adaptable templates for clichés popular with journalists and writers. For example, X is the new Y, A doesn’t know the meaning of B, and C is D’s middle name. Just replace the letters with words and you have a cliché you can use in quite a wide range of circumstances.

Wikipedia defines a snowclone as: “a neologism used to describe a type of formula-based cliché which uses an old idiom in a new context”

Here are a few examples:

grey is the new black
coders are from Mars, designers are from Venus
the only good language is a dead language
the care and feeding of small, temperamental Japanese motorcycle engines
the internet is the best thing since sliced bread
the word surrender is not in my dictionary

There are many more templates on Answers.com

The term snowclone was coined by Glen Whitman, an Associate Professor of Economics, California State University, Northridge, on 15th January 2004. There’s more discussion of this topic on Language Log.