I’m a little late to the “party” on this one, but if you can’t use it now, at least you’ll have it around four years from now 🙂
Here are my choices for The Best Resources For Learing About Leap Year:
Leap year: 10 things about 29 February is from the BBC.
10 Activities for Learning About Leap Year and Other Calendar Oddities is from The New York Times.
Top 20 craziest facts about leap years is from The Telegraph.
Why is there a leap year? comes from Wired Science.
Here are some fun photos of “leaping” marine animals.
Here are some videos:
I found this one at Richard Byrne’s blog:
And here’s a history of the modern calendar overall:
Hope you find these helpful, and feel free to offer additional suggestions.