Dictionaries and Thesauri On Line

Word Reference.com
http://www.wordreference.com/es/en/translation.asp?spen=

Merriam Webster
http://www.merriam-webster.com/

Your dictionary.com
http://www.yourdictionary.com/library/index.html

Oxford Dictionaries
http://www.oxforddictionaries.com/definition/bedlam?view=uk

Reverso
http://dictionary.reverso.net/

Thesaurus.com
http://thesaurus.com/

Free Thesaurus
http://freethesaurus.net/

Real Academia Española
http://buscon.rae.es/draeI/

Sinónimos.org
http://www.sinonimos.org/