An internet search for rainbow cupcakes will get you many recipes; I'm going to try Family Fun's recipe (that's their picture!) here.
Here's an idea that I'm going to save for future use. Pumpkin Petunia offers a cute free "Lucky Penny" printable. The way Will hoards pennies is pretty funny. I told him about lucky pennies the other day and he was all about it.
Skip to my Lou also has lots of free printables and crafts for the day here. You can find cupcake toppers, a bag topper, a pillow box (pictured below) and much more.
Of course I'm going to tell you about the pillow box. It's from Hello, Good Gravy! You first saw it on my blog here for Valentine's. And now it's back in green. Perfect for Lucky Charms or gold chocolate coins. I'm hoping to see one for Easter. Hint, hint.
Happy St. Patrick's Day! Be sure to wear your green!