Longman English Dictionary - Longman English Dictionary is the leading dictionary for learners of English of all ages and levels who want to learn more about English: definitions, idioms, examples and more
Dictionary.com - Firefox Addon - This addon searches for words using Dictionary.com, a free online service. Dictionary.com will give definitions from many different sources, including Merriam-Webster and American Heritage Dictionary, along with Dictionary.com Unabridged
Irishionary.com Irish Dictionary - Firefox Addon - Irishionary.com is a collaborative Irish dictionary. Search for words in both Irish or English. Don't worry about accent marks, as they are not required when performing a search. You are welcome to join Irishionary.com and participate in building the dictionary
South African English Spell Checker - This South African English spell checking dictionary allows you to use place names, borrowed words and expressions that are uniquely South African.
No more eina, just a lekker spell checker
Valencian Catalan Dictionary - Firefox Addon - This dictionary adds to the general version some characteristic Valencian forms, such as two accentuation possibilities of some words. For instance, anglès (general) i anglés (Valencian)
1TuDien was born with a desire Dictionary online tool ready for everyone to work or study. There are five languages for Dictionary and Interface, including: Vietnamese, English, French, Japanese, Chinese; and specialized dictionaries, directories are built and added daily. 1TuDien also supports translating with 1640 pairs of languages