To create or decipher legal abbreviations,
use the Cardiff Index to Legal Abbreviations and/or Bieber's Dictionary of Legal Abbreviations
(there is a regular and a "reversed" edition). Bieber's is available in hard copy and on Lexis (LEXREF;BIEBLA).
For abbreviations of case reporters, state codes, treaty sets, etc., you can also use the shaded pages at the end of The Bluebook: A Uniform System of Citation, the Guide to Foreign and International Legal Citations (Aspen) and/or Appendix B of Cohen's How to Find the Law.
For non-legal abbreviations, try the Acronyms, Initialisms & Abbreviations Dictionary, a similar acronym and/or abbreviation dictionary. Several of these dictionaries are on the Internet, including the
WorldWideWeb Acronym and Abbreviation Server. To find others, visit the links on OneLook Dictionaries and the Acronym
Finder.
You can look up the names of medical journals and their Medline abbreviations using the Journals page on PubMed.
To decipher the extensions at the end of corporate names ("Inc.," "Ltd.," etc.), visit the the "definitions" page posted by CI: Corporate Information.
For computer-related questions, try BABEL: A Glossary of Computer Oriented Abbreviations and Acronyms.