Lynn Viehl, over at Paperback Writer, has a great post on writing synopses - and it includes links to other sources of information, as well. One of those links, for example, is to Charlotte Dillon's collection of over 50 links dealing with writing synopses (includes examples, runs the gamut really).
What's a synopsis?
It's a chapter-by-chapter summary of your novel, written so your editor doesn't have to read your book in its entirety. Should end up between 2 - 15 pages, depending upon the size of your manuscript.
Lynn Viehl recommends you write your synopsis BEFORE you write the novel itself, one of her hints for NANOWRIMO ....