I'm told that this is an excellent resource, particularly those Polish students working with webpages in English or in MFL who want an extra hand.

A large collection of English as a Second Language (ESL) tools & resources for students, teachers, learners and academics. Browse the grammar glossary and references of irregular verbs, phrasal verbs and idioms, ESL forums, articles, teacher handouts and printables, and find useful links and information on English. Topics cover the spectrum of ESL, EFL, ESOL, and EAP subject areas.

Find out for yourself at http://www.usingenglish.com/ . 

Note: Like many of these online resources, you have to register first before you get full access.