In November of every year, there is a phenomenon called National Novel Writing Month (NaNoWriMo for short). You could submit it to the group and get their input, if you'd like. Or, you could go to a publishing house that deals specifically with the genre of your book. Is it a children's book? Go to one specializing in children's books. Is is Sci-Fi? Find one that specializes in science fiction. Not sure who does what? Go to the local book shop and root around! Pull down a few children's books and see who publishes them. Doing it this way, rather than on-line (which would, of course, be the fastest way to do it), allows you to see if you even like the kind of books they publish. If you don't like any of their publications, chances are it won't be a good fit.
Just an idea...