Arbordale: This publisher used to be Sylvan Dell. Check out their amazing science themed books.
Boyds Mills Press: An educational publisher of poetry, picture books, middle grade fiction and nonfiction.
Charlesbridge: Accepts unsolicited but wants an exclusive submission for a period of time. Several of my friends have picture books with Charlesbridge.
Chronicle Books: Not only does Chronicle take unsolicited, they take e-submissions.
Creston Books: Rotten Pumpkin is my favorite Creston Book. Be sure to check this publisher out.
Eerdmans: This is admittedly one of my dream publishers — I simply adore so many of their picture books.
Arthur A. Levine: Scholastic may be a tough nut to crack, cut this imprint takes unsolicited work. Read their guidelines and check out their catalogue.
Philomel Books: Not all Penguin imprints accept submissions but the SCBWI Market Guide details how to submit to this particular imprint.
Albert Whitman: This is another favorite. Note: They are taking e-mail, not snail mail, submissions.
Workman Publishing: This publisher has several imprints and publishes both children’s and adult titles.
This isn’t an exhaustive list but these ten publishers are enough to keep most authors busy — be sure to research each publisher before you submit your work. This isn’t to say that at some point in your career you won’t want an agent, but if you don’t have one you can still market your own work.