One of the more popular sites of this nature is rosettacode.org, which in their own words, "is a programming chrestomathy site. The idea is to present solutions to the same task in as many different languages as possible, to demonstrate how languages are similar and different, and to aid a person with a grounding in one approach to a problem in learning another."

For example: http://rosettacode.org/wiki/Hello_World

Plus, I enjoyed learning the word "chrestomathy", which "from the Greek words khrestos, useful, and mathein, to know, is a collection of choice literary passages, used especially as an aid in learning a subject."