I sometimes get requests from beginning authors and illustrators for manuscript and/or portfolio critiques. While I'm flattered, on a private level, I don't do this (except for my critique group). Nothing personal. However, on a professional level, I do sometimes give critiques - but only under certain circumstances...
For instance, at SCBWI conferences. If I am a speaker (on the faculty), I am oftentimes one of the professional critiquers made available to attendees for an additional fee (for writers and/or illustrators). You can sign up for these when you register for the conference. Professional critiques with industry professionals are usually available at every conference, so it's a great place to seek feedback - not just from me.
During our SCBWI Southern Breeze Illustrators' Day, along with the quick portfolio critiques by our visiting speakers, I will often give quick feedback to those who pull me aside. (Although I'm usually running around crazy, so it can be hard to get a moment.)
I offer portfolio critiques through ZaPow! for a fee.
Also, when I teach "Creating Picture Books" at the John C. Campbell Folk School, or upcoming in October at Binders in Atlanta, it's all about critiquing! You can sign up for my newsletter where I'll announce these opportunities.
So, if you'd like my feedback, there are ways to get it. But if I'm not available to you, you can always turn to your local SCBWI chapter. That's the Society of Children's Book Writers and Illustrators - the largest international organization of its kind and the umbrella that holds all us children's book creators together. Every region has a critique group liaison who can hook you up with other creators who are willing and available to do critiques.
There are also many former editors from major publishing houses whose jobs fell victim to the recession. Many now offer professional critique services via freelance. Again, the SCBWI is a great place to get contact information.
Everybody on this children's publishing journey goes through this process, and I wish you the very best!