The Encyclopedia of Science Fiction (3rd edition) is now in beta-text mode online for free, and even in this obviously incomplete form it's remarkable and fascinating. At Readercon this summer, in answer to the question of what works of SF criticism have been as influential as some of the seminal works of the 1970s and early '80s, I proposed the second edition of The Encyclopedia, a book that was not merely a collection of facts, but an argument about how to categorize the world and our imaginings of it. As such, it reduced even someone as taxonomy-averse as I to awe, and the influence of a lot of its idiosyncratic terms and templates on how people write about SF is undeniable.
I haven't had a chance to read a lot of the new material in the online 3rd edition, and have really only spent time with the Delany entry and the entry on Feminism. The Delany entry is basically the old entry plus some apparently quick updating -- its coverage of material by and about Delany after the early 1990s is vastly incomplete, but there's no reason to assume it will remain so. And it's nice to encounter again my favorite phrase from the older version of the entry: "frank and priapic to the verge of the scabrous" (I think "To the Verge of the Scabrous" would be a marvelous title for something...).
The Feminism entry, originally written by Lisa Tuttle, has been updated by Helen Merrick, a great choice for that task. (The entry on "Women in SF" does not seem to have been updated yet.)
(Tangentially, it seems to me it would be helpful to have the contributors page more prominently available. All the abbreviated names of contributors are annoying enough without hiding the page that tells us what the abbreviations mean. It would be nice in the future if the contributors' initials could provide the full name when hovered over. The people who've done all this work deserve credit.)
Just moving the original encyclopedia, with all its references and cross references, onto the internet is a gigantic task. That the team has worked and continues to work on updating it is even more impressive, since it's not like history and the publishing world are going to stop and wait for them to catch up. Even in its current state, it is easily among the most useful reference sites available anyone with an interest in science fiction. I'm very excited to see where it will go from here...