wiktionaryis a wiki based open content dictionary
an online medical dictionary
Australian slang website lists localised language for those in Australia
for astrobiological terms
net lingo online dictionary
can't think of the right cybernetic term? check the cybernetics web dictionary..
dictionary.com - a good resource to quickly check spelling. http://www.dictionary.com
reverse lookup dictionary - search for a concept and this site provides a list of terms. it's great for those 'the word is on the tip of my tongue' moments. visit http://www.onelook.com/reverse-dictionary.shtml to try it