FamilySearch is the premiere free source for genealogy documents. With millions of records from around the world, its collections cover all 50 states and many countries. The wiki has pages for countries and localities down to the local level. Registration is free and allows you to upload a tree, save documents to source boxes, edit wiki pages, and more. Additionally, since FamilySearch is a resource of the LDS church, the website can be used to order physical items from the Family History Library in Salt Lake City, Utah, to your local Family History Center for a fee. Volunteers can help index records, which allows them to be searched. Although many records are searchable, FamilySearch has a vast collection of image-only records that can only be browsed.
FamilySearch.org
FamilySearch.org