The Public Library of Law (PLoL) offers cases from the U.S. Supreme Court (1754-present), U.S. Circuit Courts of Appeal (generally 1951-present, with a few exceptions), and state cases (1997-present).
You can perform a keyword search of all the resources via the search box on the front page, or limit your search by selecting the “Advanced Options” link underneath the search box. The Advanced Options search allows you to limit by court and by date. In addition, the PLoL provides a “finding a case” tutorial External for visitors, linked on the homepage. Users are required, however, to sign up for a free account in order to see their results.