The Indiana University-Purdue University (Indianapolis) Library offers a browseable list of U.S. Government acronyms and their definitions.

The library also offers a guide to Military Acronyms and Glossaries – a metasite listing a variety of resources for decoding military terms.

For definitions to more generally-used acronyms see:

• Acronym Finder Offers Definitions of Over 215,000 Acronyms & Abbreviations