The Williamsburg Libraries

Genealogy Sites

ancestry.com - the most popular genealogy website.
genealogy.com - the name says it all.
Family Search - supported and sponsored by the Church of Jesus Christ of Latter-day Saints.
My Heritage - Focuses on genealogy community building and networking.
ProGenealogists - Professional Genealogists at the Family History Library. They have an excellent list of websites.
Cyndi's List of Genealogy Websites - hundreds of thousands of links, all categorized, including Massachusetts links, with many subcategories.

Family Chronicle - The "How To" Genealogy Magazine. Of course they have their own set of links.
Family Tree magazine, with a categorized list of sites.
Genealinks - also has a list of Massachusetts genealogy links.