English online dictionaries

English - Hungarian (bilingual) dictionaries

http://szotar.sztaki.hu/angol-magyar

http://angol-magyar-szotar.hu/

http://dictzone.com/angol-magyar-szotar/

Useful phrases and topical collections

English (monolingual) dictionaries

http://dictionary.cambridge.org/

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

http://www.thefreedictionary.com/

http://dictionary.reference.com/

http://www.ldoceonline.com/

http://www.oxforddictionaries.com/

http://www.collinsdictionary.com/

Picture dictionaries

http://www.esolhelp.com/online-picture-dictionary.html

http://www.learnenglish.de/vocabpage.html

A great collection: