Amazon is always a good resource when researching any publisher. Just do an advance search and plug in the publisher's name. If they're a big publisher, it's better to select a limited number of years back you'd like to view. Five years or so is usually enough to give you an idea of the type of books that house publishes.
It's helpful when, say, you're researching picture books and you want to find out if they do lots of animal books, or books with cumulative structures. I'll often copy a chunk of a book's info page, including the cover art, then save it into a text file. I sometimes do that when I'm researching publishers who might be a fit for one of my manuscripts. You might not want to pitch to publishers who have produced a book which is TOO much like your current book, (say, a rhyming book about dancing kumquats), but if it's a publisher who does rhyming books, or books about anthropomorphic... er... fruits, you've got a better shot.
Sometimes it can be frustrating, finding a publisher which is a good fit without being TOO good a fit. In my crit group, we all laughed (instead of crying) over a rejection one of us received from Viking which said, "It's great, but we already have a book about blueberries."
Uh. Yeah. That would be Blueberries for Sal. Published SIXTY YEARS AGO. Seems like they could take a chance that kids who read it have moved on. Maybe when a book becomes an icon like Sal, publishers steer clear of ever touching such a subject again. Who knows.
But on the whole, it's a good thing to find houses which have previously published books similar to your own, and Amazon is a quick(-ish) way to do it. Once I've copied a few similar books into that text file, I store it in a folder with the manuscript, titled "Target markets for XYZ (title of the book.)"