1) The Encyclopedia of Science Fiction, Third Edition. The first two editions were essential enough; the third edition may not yet be Wikipedia but it is already more authoritative and in admirably ambitious. It's not a completed work; voting for it in this state it feels a little like giving Barack Obama the Nobel Peace Prize (I hope with a better outcome); but it gets my top vote anyway.
2) The Steampunk Bible: An Illustrated Guide to the World of Imaginary Airships, Corsets and Goggles, Mad Scientists, and Strange Literature. A beautiful book from which I learned more than I had expected.
3) Writing Excuses Season 6. I didn't vote for this last year because I could not bear to download and listen to three hours of advice on writing sf from enthusiastic authors whose works I haven't really warmed to. This year I found the transcripts which made it easier to form a judgement. I've read the first quarter of the season and feel it's a decent effort, but I'm just not in the target audience.
4) Jar Jar Binks Must Die... and Other Observations about Science Fiction Movies by Daniel M. Kimmel. It's decent commentary on sf cinema, which pointed me in some interesting new directions. But a book of essays written at different times over a decade inevitably loses some focus.
5) No Award.
6) Wicked Girls by Seanan McGuire. I'm sorry, I enjoyed this very much but I just don't think it is eligible. The rubric for this category is: "Any work related to the field of science fiction, fantasy, or fandom, appearing for the first time during the previous calendar year or which has been substantially modified during the previous calendar year, and which is either non-fiction or, if fictional, is noteworthy primarily for aspects other than the fictional text, and which is not eligible in any other category." This is an album of songs which all describe more or less fictional situations, of which a bit more than half have more or less clear fantasy elements in the narrative. In so far as the songs themselves relate to the field of science fiction, fantasy, or fandom, it is precisely in their fictional content. Agreed, the lead singer / writer is an author and fan who has three other Hugo nominations in different categories this year; but that seems to me far too slender a thread to justify nomination in this category, let alone voting for it. I liked it a lot but it drops off my ballot.
See also: Best Novel | Best Novella | Best Novelette | Best Short Story | Best Dramatic Presentation (Short Form) | Best Professional Artist | Best Fan Writer | Best Fan Artist | Best Fancast | The John W. Campbell Award (Not A Hugo)