So I am going on record here today. If I had to pick only one resource for each of these genres, this is what I would use and why.
Mystery: This is the easiest one. When I have a mystery questions the first place I go is Stop You're Killing Me. I cannot say enough about how helpful and useful this site is, so I will let them tell you...
Stop, You’re Killing Me! is a resource for lovers of mystery, crime, thriller, spy, and suspense books. We list over 3,300 authors, with chronological lists of their books (over 37,000 titles), both series (3,700+) and non-series. Use the alphabetical author and character links above or the special indexes in the left column. And it’s perfectly fine with us if you print our pages for your private use, especially for a trip to your local library or bookstore.Psychological Suspense: From the easiest (Mystery) to the most difficult now. Psychological suspense is not a recognized genre, but rather, these books are part thriller, part horror, and part mystery. Psychological Suspense is very popular with a wide range of readers, but it can be hard to find on the shelf. I know because the mini-genre study I did on the BPL's psychological suspense holdings is constantly being recopied. We don't have that document up on the website yet, but until then, you can use this psychological suspense page from the always trustworthy Hennepin County Library.
Science Fiction: If you have any SF question, stop and immediately go to Locus Magazine Online, the online version of the leading news and review magazine of the science fiction, fantasy, and horror publishing fields. I use Locus Online as a portal to every conceivable SF link. It has never let me down.
Literary Fiction: Here you go right to The New York Times Books Section to find links to the notable books lists, their blog Paper Cuts, and of course tons of reviews of literary fiction titles.