West publishes a series of case "Digests" covering a jurisdiction (e.g., the Federal Digest or the New York Digest), region (e.g., the Atlantic Digest), subject (e.g., the Bankruptcy Digest) or date range (the Decennial Digest). Each Digest provides summaries of the relevant published judicial decisions. The summaries are organized according by West Key Numbers. (For a discussion of the West Digest System, see Barkan, Mersky and Dunn's Fundamentals of Legal Research.)
You'll find at least the Federal Digest and the local state or regional Digest in most large law libraries located in a state that has a Digest. You'll tend to find more Digests in the larger academic libraries. Local law firm libraries will generally lend Digest volumes, while academic libraries will generally provide copies of select sections.
Alternatively, you can recreate any Digest set using Westlaw. You do this by clicking on the "Key" icon or going into the "Key Number Service" or maybe something else if you're using yet another version of Westlaw. Call Westlaw (800-733-2889) for more specific assistance.
To find out if a state has a digest (e.g., Texas does, Delaware doesn't), you can look up the state in the Legal Information Buyer's Guide & Reference Manual or a similar directory, or you ask a reference librarian in an academic (or other large) law library in that state.
Note: It can be extremely difficult to borrow out-of-state Digests. Unless the state in question is contiguous to yours, you're generally better off getting copies or using Westlaw.