AltLaw is a web searchable database of federal court opinions.  Pretty handy.  Here's what it says about itself:

AltLaw is a joint project of Columbia Law School’s Program on Law and Technology, and the Silicon Flatirons Program at the University of Colorado Law School. AltLaw was written by Stuart Sierra and Paul Ohm, with help from Luis Villa, and produced by Tim Wu.

For most courts, opinions are available from mid 1990's to April of 2007, and recent opinions should be available soon.  Before long, the site expects to be able to offer opinions within 24 hours of publication by the courts.  More from the site:

The law is meant to belong to the people, but it can be surprisingly hard to find. Case reports, a major part of the laws of the United States, are hard to get at, and even when on the Internet, rarely searchable. To get full access you generally need either a library of law reports, or an expensive subscription to an online database, which can cost hundreds of dollars per hour.

AltLaw is a small effort to change that—to make the common law a bit more common. AltLaw provides the first free, full-text searchable database of Supreme Court and Federal Appellate case reports. It is a resource for attorneys, legal scholars, and the general public.

Features

• Full text search of the last decade or so of federal appellate and Supreme Court opinions.
• Advanced search options (proximity searching, Boolean, concentration, wildcards, etc.)
• Fast and free
• Updated daily (not yet, work in progress)

Limits

• Coverage, for most Circuits, limited to about the last 10 to 15 years.
• West Reporter Citations (i.e., 23 F.3d 178) not yet available (work in progress)
• As of yet, no state law or district court cases.

Watch out Westlaw and Lexis . . ..