I generally add links to online Greek resources to the sidebar, but as this is a commercial product for sale, I've decided not to add it there. Nevertheless, over on Deinde Danny Zacharias has just made available the catchily (and descriptively) named NT Greek Vocabulary Expansion Packs, available here. I will post a response to the Expansion Packs in a couple weeks. But at a mere $8.00 (with an offer for $8 off Flash! Pro [for PC users], making the Expansion Packs free), some of you might find it worth the cost to try these out on your own.
[NB: David Alan Black has provided free online flashcards for his first year Greek Grammar Learn to Read New Testament Greek (see the link on the sidebar). Danny's Expansion Packs are keyed to four different first-year grammars, including Black's.]