I've never read Romeo and Juliet before, but I feel well acquainted with the story. Of all of Shakespeare's plays, this one seems to have worked its way most thoroughly into many different levels of culture.
The first thing I think of when I think Romeo and Juliet is "cliche".
The second thing I think of is a movie called The Magical Legend of the Leprechauns. Despite the frame story dominated with annoying humans, I enjoyed this imaginative Romeo and Juliet retelling.
Then I think of West-Side Story and the Hindi version Josh (I've only seen the Hindi version).
While thinking about Indian references I think of a song in the first Telugu movie I ever watched, Bommarillu.
Also, Romeo and Juliet was also the play the characters in the second Hindi film I ever watched, (Kuch Kuch Hota Hai) were studying in their English class.
As far as books I've read... Romeo and Juliet is also referenced in the second Twilight book, New Moon. She actually makes an interesting question "what if" question based on the play.
Another book I've read which is fairly clearly inspired by Romeo and Juliet is Son of the Mob. Where a mob boss's son falls in love with the daughter of a police chief (or perhaps it was a detective, I don't remember anymore).
But this is not even a significant fraction of different places Romeo and Juliet have gone. It's just a few of the first things I think of when I think of Romeo and Juliet.
