Acronym Finder
Find out what OPEC, ASEAN, NATO and over 100,000 other acronyms stand for. The site covers abbreviations and initialisms, too.
http://www.acronymfinder.com/

Acronym Search.com
Your online source for acronyms and abbreviations.
http://www.acronymsearch.com/

Acronym Server
Search here for acronyms and for words used in acronyms.
http://www.ucc.ie/cgi-bin/acronym

Ask Oxford
A guide to emoticons and acronyms used in emails, text messages and online chat.
http://www.askoxford.com/betterwriting/emoticons/

Berkeley University
A dictionary of abbreviations and acronyms used in geographic information systems, cartography and remote sensing.
http://www.lib.berkeley.edu/EART/abbrev.html

CGI Morse Code Translator
As the title states.
http://www.scphillips.com/morse/trans.html

Dictionary of Symbols
Online symbolism dictionary.
http://www.umich.edu/~umfandsf/symbolismproject/symbolism.html/

ISO 639-2
Three letter language codes.
http://www.id3.org/iso639-2.html

Morse Code Alphabet
The international Morse code characters.
http://www.babbage.demon.co.uk/morseabc.html

Nato Phonetic Alphabet
Familiarize yourself with one of the most widely used phonetic alphabets in the world, which is used regularly by the travel industry.
http://www.dynamoo.com/technical/phonetic.htm

The Acronym Database
Find out what all those letters stand for.
http://www.ucc.ie/acronyms/

US Postal Service
Officially recognized postal abbreviations.
http://www.usps.com/ncsc/lookups/abbrev.html

Wikipedia
An introduction to Morse code.
http://en.wikipedia.org/wiki/Morse_code