Playdough is relatively simple to make. I know that a lot of people do a pretty basic salt dough for playdough, like the one found here. However, I found a recipe through one of my all time favorite crafty blogs that I just LOVED. I made this stuff over 3 weeks ago, and it's still soft and pliable. Amazing! I KNOW!!!
You can find the recipe and detailed instructions here. Oh, and the craft blog I love? It's called Homemade by Jill. She hasn't blogged as much since the birth of her 2nd baby, but it's only been about a month. She's got her hands pretty full.
Have fun with the playdough!