Perhaps some of you reading this are interested in the history of fantasy and science fiction, either to satisfy your own curiosity, or for academic reasons. Regardless of why, I'd like to call your attention to an excellent resource that is now available for free online.
John Clute and John Grant edited The Encyclopedia of Fantasy in the 1990s. It has been updated through 1997, and is now available online for free, joining The Encyclopedia of Science Fiction (which is more up-to-date, and expanded). Both are terrific resources, and I highly encourage you to take a look at them.