- The University of Washington Law Library provides an alphabetical listing which focuses on U.S Legal Abbreviations. URL: http://lib.law.washington.edu/pubs/acron.html
- Cardiff University in Wales provides a larger list and a search by title feature covering world legal abbreviations. URL: http://www.legalabbrevs.cardiff.ac.uk/
- Monash University in Australia also provides a comprehensive list of world legal abbreviations including U.S. cites. URL: http://www.lib.monash.edu.au/legal-abbreviations/abb-a.html
I have primarily used Cardiff for my legal abbreviation needs, but I plan to take a look at the others Robert recommends.