Google Book Search
Google Book Search has drawn fire for stepping on the toes of copyright holders, but it's the public-domain works Google has scanned that genealogists will perhaps most enjoy. By using the Advanced Book Search page and selecting "Complete books only," you'll guarantee that the books appearing in your search results will be viewable cover to cover. Searching for "vital records" turns up VRs from dozens of Massachusetts towns. The first result for "genealogy" is a book about one of my own lines, the Coolidges. Search with "All books" selected to view sample pages of copyrighted works, including other genealogist-enticing titles.