Fantasy author Joshua Palmatier got tired of fielding the same questions phrased slightly differently about how to write synopses, and decided to follow the writing maxim of Show Don't Tell. So he convinced a whole bunch of writers to post examples of synopses that sold.
The examples include fantasy, romance, and science fiction stories, and even one Hollywood screenwriting synopsis.
I posted not only the synopsis for Raven's Heart, the first novel I sold (although it was the third one I wrote), but also the original ending that didn't sell. When you compare the two, the flaws in the original are obvious. People do things for no reason, events hang upon coincidences, the hero is selfish (and shows all the emotional sensitivity of a future spouse abuser) and the heroine's fate is determined by the men around her. By the time it was rewritten and sold, however, everything happens for a reason, the hero is willing to sacrifice everything that matters for the heroine, and everyone around her waits eagerly for her to make a decision that will tell them how to proceed.
I also posted a Question and Answer interview regarding my synopsis writing style. I actually like writing synopses, because they let me make my mistakes early in the process. It's a whole lot easier to change a few paragraphs in a synopsis than it is to throw out and rewrite entire chapters in the finished book.