Here is a how-to video about marshmallow fondant. A friend is trying it out for the first time and wanted me to show her how...since I'm stuck in my house all day, I thought this might work! All instructions are outlined in the video, even the recipe, which is:
4 C unpacked mini marshmallows
2 T water
3 to 4 C icing sugar (confectioners sugar)
One thing to note about marshmallow fondant, as opposed to "regular" fondant, is that it IS more prone to tearing especially if you get it on the thin side, or if you've incorporated too much icing sugar. However, to me, the cost (value) and the taste (yum) make this fondant the way to go for your everyday endeavour!