Spelling dictionaries

Dictionaries of Polish Scientific Publishers PWN

Dictionaries of foreign words

Cambridge Dictionaries online - the most popular English online dictionary.

Longman Dictionary of Contemporary English - Longman Dictionary of Contemporary English.

MEGA Słownik - Project of  online Dictionary which allows to use the following dictionaries:

• Polish - synonym and antonym,
• English-Polish-English,
• German-Polish-German,
• Russian-Polish-Russian,
• French-Polish-French,
• Spanish-Polish-Spanish,
• Italian-Polish-Italian,
• Swedish-Polish-Swedish,
• Dutch-Polish-Dutch,
• Croatian-Polish-Croatian,
• Ukrainian-Polish-Ukrainian.

 Merriam-Webster - online access to American English-English Dictionary.