Slang-Dictionary.org: A collection of slang dictionaries which
presents you with a vast array of slang words and expressions, ranging
from older and internationally-recognised slang to modern day coinages,
colloquialisms, vulgarities and many other non-standard usages of the
English language.
Tiscali.co.uk: Hutchison Dictionary of Difficult Words. Search the Hutchinson Dictionary of Difficult Words' A-Z index of over 13,900 difficult words to increase your vocabulary or just find out what those words really mean!