Is there a website that lets you plug in a bunch of your favorite authors and based on that suggest others?

I know it seems like a pedestrian answer...but I'd suggest amazon.com. Just go to a book you like and explore the tags and other people's lists.

I would agree with Amazon. Or LibraryThing or http://www.literature-map.com/

If your library subscribes to one of them, try either What Do I Read Next? or NoveList. They're both databases where you can enter either books, authors, genres, etc you've read and get recommendations based on them. Most libraries have home access for many of their online databases, so you won't even have to go in (unless you don't have a card).