Came across this very cool post on StumbleUpon: 25 greatest Sci Fi novels ever. Check it out and see what you think. Nice summaries and engaging graphics.
Here is another list of great Science Fiction, though the presentation is not as appealing.
I had the great fortune of actually studying under and interacting with James Gunn, one of America’s most accomplished Sci Fi writers, and historians. You can read more about that and see a short video of him on my About Page.
Both these lists are great starting points for anyone who wants to hone their craft and develop their skill writing science fiction.