I have a few Hanafuda decks on hand, but if you don't have any yet you may want to think about grabbing these Mario themed ones at the Nintendo store in New York City. As per the official Twitter account they're in stock for $20, which is about the same price you'd pay if you imported them -- you just don't have to wait weeks for free international shipping.
Whenever someone wants to learn how to play a Hanafuda game, I always point them to the same spot -- this wonderfully designed website that's a little dated, but gets the job done. It'll teach you how to play Koi Koi, one of the most popular variants, with an easy to read explainer and an interactive flash version.
At some point in your life consider ordering a pack (Nintendo or non-Nintendo related) and watching this short video doc, if only to learn a bit of Japanese culture.
Nintendo NY [Twitter]