I got an email from a non-library friend wanting to know if there is a prominent publisher for the young adult market -- she knows someone who might want to publish someone, and she's trying to help.
As usual, I didn't answer the question directly but I did refer her to two other sources which would be useful.
One is the Literary Market Place (aka LMP) -- it comes out every year and is a directory of publishers in the US. You can find detailed info about various publishers, and in the middle somewhere is a huge directory of US Publishers by Type of Publication. Look for Children's Books & find GOBS & GOBS of them. Then refer to the detailed info. for publishers to see if they'd publish what's called "Young Adult" literature (for teens & tweens). The entry for Blooming Tree Press, for instance, gives you the page number for the main entry -- which then gives you contact info, email addresses & web sites, # of titles published per year, and a short blurb about what they publish.
There's also something called the Writer's Market, which has essays & suggestions on how to get published, as well as a directory of publishers. In the back is a subject index, which refers you to publishers that address "Children's / Juvenile" books. You get more info. in the directory -- like editor's names, how much royalty they pay, and a few recent titles.
Most public libraries have both of these books. Happy writing!