The Chocolate Muffin Tree where they made "tie-dye" Easter eggs (they used washable markers and sprayed them with a water bottle--a super fun idea!) and the other from the Mom to 2 Posh Lil Divas blog where they made hearts with the same technique we used below.
The only tip I might add to this is that the dot markers didn't go all the way through the coffee filter when we folded it in quarters. We had to go over the pattern a couple times. So I suggest either folding it just in half or not folding it at all. This project could definitely be used for just about any shape/holiday! My 6 year old especially loved this one and even made more of them with her friend during a playdate.