Project Gutenberg is a non-profit organization that digitizes books that are in the public domain. They provide their 42,000 books for free in a variety of formats including pdf, epub and Kindle. It's like a virtual library that you can browse. Love it!
Google Books is heaven to researchers. My partner, Lisa, introduced me to this incredible site/tool and I visit it several times a week. Beautifully designed and very easy to use.
Locus Online is the web version of the famous scifi magazine of the same name. I know of no other site that covers scifi and fantasy so thoroughly. I love the reviews and the just published sections.
Book Riot a sight I visit daily. The articles and reviews are current and often challenging. You won't find a lot of main stream puffery here. I Highly recommend this book site.
Librivox is the audio version of Project Gutenberg. Thousands of audio books are listed here. I've contributed to several projects myself.
Lisa Morton, is a six-time Stoker award winning horror author. She's edgy, contemporary and unafraid to mix genres and deliver some good solid scares. I love her work.
NPR books covers all kinds of books in all kinds of genres. I like their podcasts and their website is very well designed.
Dark Delicacies is the only bookstore I know of that deals exclusively in horror. Located in Burbank, CA., they have an amazing amount of signings and horror-related books, perfumes (yes!), toys and clothing.
Two Dollar Radio is a co-op publisher of some of the most interesting new fiction you'll find anywhere. I've discovered many remarkable authors here. Their books are beautiful,too.
Kirkus Reviews very interesting. Found a lot of good books browsing this site. This is a well-designed website with excellent writing.
Lynn Munroe issues regular catalogs of vintage paperbacks + a good dose of history and author/artist profiles. His contributions to the history of the vintage paperback are huge. AND his prices are reasonable. Lynn is an unsung hero in my book. Highly recommend his website