In the Glee episode "Bad Reputation", it was Santana Lopez who posted the "Glist" around the school.
In the episode, the "Glist" was a list of the most promiscuous students at McKinley High, and Santana posted it around the school as a prank. However, the prank backfired when one of the students on the list, Rachel Berry, was humiliated and ostracized by her peers.