I had figured that with all the SF fans on this board that someone would have mentioned Locus Magazine's online poll for the best of 20th and 21st Century in science fiction and fantasy. Locus is the oldest and probably best of the magazines covering SF & F--I've read it since the seventies.
You can find their main site at www.locusmag.com
and the poll site itself is at http://www.locusmag.com/temp/2012All...llsBallot.html
and will be open until November 30.
This isn't just novels, folks, but also novelettes and short stories. There are also separate "suggestion" pages to remind you of items you've forgotten or to place your votes in the right century.