There are a lot of great websites that contain important information on the Hugo and Nebula awards. Here are some of the best:
The Long List of Worldcons contains some great attendance data for the Worldcon (they award the Hugos.
Here’s one of my posts on Declined Hugo and Nebula and Other SFF Nominations.
And here are some my blank Hugo and Nebula data sets, so you can run your own stats.
Here are some various pre-existing analyses of the Hugos and Nebulas that I’ve found interesting and helpful:
Nicholas Whyte’s website: Whyte has some interesting breakdowns of the Hugo and Nebulas by age, by joint wins, and other data. He also blogs quite frequently, including about various SFF awards, at his website.
Jed Hartman’s Gender Breakdown: Hartman has some great data on the Hugo and gender demographics, that spans all the Hugo fiction categories, not just the novels. Updated yearly.
Dreaming About Other Worlds: Aaron Pound also gives a comprehensive look at gender in the Hugo awards in this post.
Staffer’s Book Review and the Voting System: Justin Landon provides an excellent breakdown of how the Hugo preferential voting system works, as well as a sharp analysis of the 2014 awards. Langdon also provides a useful take on the 2013 awards.
Jo Walton’s Revisiting the Hugos Series: Walton provides a detailed analysis of every Hugo award from the beginning (1953) to 2000.
Pew Research has a good “snapshot” of American reading habits for 2013.
I’ll add more links as I come up with them. If you’ve know of anything I should add, let me know.