Abbreviations.com can be searched and browsed. There are over 230,000 entries and 81 categories such as business, medicine, science and international abbreviations and acronyms.
Acronym Finder is a searchable dictionary of over 330,000 acronyms, abbreviations and initialisms on the Internet.
3,097,000 Acronyms and Abbreviations. 2,950 Topics.
GovSpeak: A Guide to U.S. Government Acronyms & Abbreviations
The most current, extensive and fully-linked listing of U.S. government agency, office, program and publication acronyms. This guide was created by the University California at San Diego.