Here is a master list of all of the FREE Polish learning resources online.
I put together what I believe is a comprehensive list of all of the free online resources to learn Polish (DUO is at the top of course), including video, podcasts, apps, courses, dictionaries, websites, textbooks ... you name it. The complete list is here: http://gratisglobal.com/learn-polish-free/
If I missed anything at all, please let me know so I can add it. My criteria are that the resource must be free, useful and high quality. I do include apps and programs with the "freemium model" as long as the free offering is substantial enough.
Hope this is helpful.
I find the verb conjugation tables on the Tasting Poland website very useful. http://www.tastingpoland.com/language/verb/verb_infinitives.html
I suppose, that you should definitely add http://sgjp.pl to the list of dictionaries. Grammatical Dictionary of Polish Online lists all the grammatical forms (conjugation, declension etc., including archaic and rarely used forms) of over 334 000 Polish words. A detailed description is here. It does not list only typical dictionary entries, but also many proper names (eg.: piątek: day of week, male family name, female family name and geographical names like Limanowa or Murzasichle). It lists also many potential forms, that are not used in everyday speech (like the adjective niećmi which means inappropriate for a moth or not mothlike). Its usefulness for for the learners of Polish cannot be overstated, given the complexity of Polish inflection. The only minus of this dictionary is that it has almost no word definitions. It has Polish and English interface.
Next great dictionary is https://sjp.pwn.pl/ - it is more than just a dictionary: It contains 3 dictionaries: online version of Dictionary of Polish Language PWN (Edition 2005, 100 000 entries), The Great Orographic Dictionary PWN (Edition 2017, 140 000 entries) and Dictionary of Polish Language by prof. Doroszewski (Edition 1969, containing roughly 125 000 entries) - the last is old, but very valuable source of collocations. Besides it contains a Corpus of Polish Language, Encyclopaedia, the complete set of Polish Grammar rules, and tons of explanations in the Language Advisory (Poradnia Językowa). The only disadvantage is that it is all only in Polish. And it does not contain the inflection tables - only lists these basic forms of given word that are irregular (if any).
Another great dictionary of Polish is http://wsjp.pl/ - it contains "only" 35 000 entries, but it contains word definitions, collocations and inflection tables (only modern language forms). This one is a "work in progress", but still it is great. Attention - it is not a Polish-English dictionary - it is just Polish, with all the explanations in Polish.
Another valuable resource is http://nkjp.pl/poliqarp/ - The National Corpus of Polish, including complex search system. Can be switched to English interface.
And https://synonim.net/ - a thesaurus of 600 000 synonyms for 150 000 words.
Is the spelling of "earn Polish" intended? :P
Another great list with additional resources, including clozemaster itself: https://www.clozemaster.com/blog/best-resources-for-learning-polish/