Here's a website I've found tremendously useful and to which I have subscribed. At its heart is a collection of self-reported data about announced book and other literary rights deals. Most of the announcements identify the players, title and genre, and some give a coded identifier to indicate what range the deal falls into in terms of dollars.
I used its rankings of agents within genres (the site will give you both most-deals and most-six-figure-deals lists), together with some judicious googling, to create a list of agents to query, and that's how I got in touch with my agent, Peter. For this it was absolutely priceless; it not only generated a list of agents but also helped me get a sense of which agents were "good" ones and for what.
I also get the site's daily e-mails announcing further deals and other industry news. These are tremendously helpful for keeping tabs on what the current and upcoming markets are, as well as trends in bookseller bankruptcies, e-books, etc.
Caveat: the data is self-reported, and therefore incomplete, maybe even dramatically incomplete. Still, I have found it powerful, so I pass it on as a tip.