lexisONE is a free service from Lexis Nexis Butterworths in the US. It is designed for small law firms, and provides lots of useful free resources:
It holds US case reports from the US Supreme court, going back to 1790, and the previous five years of reports from the Combined Federal Cases, 1st-11th Circuit Courts of Appeals, the District of Columbia Circuit Court, Bankruptcy Appellate Panel and the Federal Circuit Court of Appeals.
You can search by name, by subject, or by court, and it will provide the citation and a plain text version of the case.
You can then choose to pay to ‘Sheperdize’ the results, Shepard’s® Citations Service, which costs $6. This is the way to check whether the case you have found is still good law (ie check the judicial history).
lexisONE also provides access to over 6,000 US Court Forms, for free, covering a range of jurisdictions and topics; a Legal Web Site Directory, with links to state and federal resources, codes, law firms etc; and also articles and an alert service.