I love this site. It's put together by the author Brenda Hiatt and is her way of giving back to other romance authors. It is an anonymous listing by authors of what publishers across the board have paid various authors from different publishing houses.
It's a great resource for when you are trying to decide what to shop at which place and a way you can realistically determine what you have a chance of making there. While the numbers and mileage vary per book and author I have found the information on this site to be pretty accurate.