Shipping companies and warehouses sometimes have free pallets. Craigslist.org may have listings for free pallets. Animal feed and farm supply stores are another valuable resource.
Garden supply shops use a lot of pallets and may give some away. Facebook pages dedicated to recycling or trading may have postings for free pallets. Large retailers such as Lowes and The Home Depot are not good sources, as they often return pallets to their shipping companies.
Wood pallets have been banned from landfills in many areas. This makes it easier to find free ones. Sometimes pallets are made of woods other than pine. These can be used to make many beautiful craft projects.