How many projects do you work on at one time?

I'm feeling a bit overwhelmed right now. I have so many writing projects that I want to do. I'm working on a children's fiction book, a nonfiction Oklahoma History curriculum, and a fiction mystery/romance, as well as keeping up with my Web site, marketing my books, and writing blogs, books and iPhone reviews and newsletters. Where does my time go?

How do you prioritize and schedule your writing time?