Since I enjoyed the first one so much, I should mention that Frantic has a sequel, which is also the current card challenge. I have yet to decide if I like it as much as the original. There is more there, but adding achievements and such makes it feel less pure.
Full disclosure: if you use one of those links and sign up at Kongregate, I get some kind of points that do nothing but put a number by my name. But, you know.