Translation:The computer is very useful at my work.
sjp.pl is also good for verifying whether the word is listed in at least one of the few chosen dictionaries and also give you the list of inflections, but many words are not defined and the inflections are not categorized in human-readable way. It's auto-generated for use in Scrabble-like game.
dobryslownik.pl is also a work in progress (and new words are included by subscribers' request). In its free version it can show you even some "controversial" forms like „póki co” or „Gienek”.
miejski.pl is basically Polish version of Urban Dictionary
pl.wiktionary.org can give you full inflections and definitions for some words, as long as you trust the userbase