We feel it is important to recommend good materials and sources from our experience dealing with vendors.
Amazon books is always prompt and professional with good prices for children's literature.
The National Women's History Project has some wonderful literature and classroom activity books for use in mathematics and science instruction. For professional literature, we have found NCTM 's Research Ideas for the Classroom to be both readable and filled with valuable ideas for teaching mathematics. We have used a variety of suppliers for mathematical manipulatives and laboratory supplies, with varied experiences. Science Kit is an excellent source for science supplies.