Where you buy your materials will depend upon what you’re looking for and the type of homeschool method you have chosen. I recommend checking Rainbow Resource once you know what you want to buy. Many times they’ll have the item cheaper than anywhere else. Some of the different suppliers of homeschool curriculum are as follows:
Math U See http://www.mathusee.com/
Rainbow Resource http://www.rainbowresource.com/index.php
Handwriting Without Tears http://www.hwtears.com/
Discount Homeschool Supplies http://www.dhss.com/shop/
Rock Solid Inc. http://www.rocksolidinc.com/
Another idea is to look for places that sell used curriculum. Websites such as www.amazon.com; www.ebay.com; www.half.com and www.homeschoolgatheringplace.com are a few you can look into.
Homeschool conferences are a good place to see and review different curricula before purchasing. You may also wish to ask fellow homeschooling families to allow you to view the materials they use so that you can see before you buy. A good place to read reviews of materials is http://www.homeschoolreviews.com/ .