Browse through the list of plans on the Woodworkers Workshop website. This site offers links to free plans from several different websites, allowing you to find what you're looking for all in one place. Most of the plans listed are for rocking or hanging cradles, with a few cribs thrown into the mix as well.
Look at the patterns listed on the Free Woodworking Plans site. This is similar to the Woodworkers Workshop site, but with a wider variety of baby furniture types, with fewer plans in each category. The site includes plans for cribs, cradles, high chairs, changing tables and numerous types of play furniture from forts to wooden vehicles.
Purchase plans from a commercial website if you prefer to use a professionally made pattern. The two most prominent companies in this category are Rockler and Woodcraft. Rockler offers several crib and cradle plans, while Woodcraft includes a wider selection with changing tables and seating for small children.