Google Scholar: select "legal opinions and journals" (or, on the Advanced Search page scroll down to select for searching a particular state's court opinions, or only federal court opinions.) Includes state case law from 1950 forward and federal case law from 1923 forward,
LawCite : a citator for cases and law journal articles.
Law.com Quest. A searchable database of items in the "law.com network" (IncisiveMedia publications, with full-text access for subscribers only) and in the "legal web" (law firm websites and legal blogs).