I just received my flashcards from Inside Story and they are wonderful! All kinds of fantastic words, illustrated by cats and dogs in one set, animals of all kinds in another, and the city of Seattle in a third set.
There are more than 900 free, printable flashcards on the website as well. They range from cards for Kids and English Learners (Basic and Easy) to SAT words (Medium) all the way to words for the GRE and beyond (Hard). You can hear the words pronounced, study the words by hiding the definition, or print the cards. New words are added often, according to the website.
I learned something while perusing the Hard words—I am NOT an Ailurophile, a person who likes cats. However, I DO love them in their hilarious poses on these cards!