English language:
www.britishcouncil.org/croatia
www.askoxford.com
www.merriam-webster.com
www.rjecnik.net

German language:
www.goethe.de
www.kulturforum-zagreb.org
www.duden.de
www.dict.cc

Croatian language:
www.eudict.com
www.erjecnik.com/#rez

Russian language:
www.yandex.ru
www.gramota.ru
www.sussex.ac.uk/Units/russian/Ruslang/
www.russianlessons.net
www.practicerussian.com
www.rambler.ru
www.masterrussian.com

Other:
www.freedict.com
www.eudict.com
BBC.com
ALBIS
Babelfish
http://www.turkishclass.com/
http://www.kypros.org/LearnGreek/