I believe most agents and editors, and some writers, have subscriptions to Publishers Marketplace.
www.publishersmarketplace.com
They send out a daily newsletter called Publishers Lunch that highlights book deals and news in the industry. There is a cost to subscribe. They do send out a free daily version of the newsletter, but it doesn't contain as much information as the paid version (of course

).
One of these days I'm going to go the paid route...

For now I get the free one, and I find out some things, sometimes.