Here's a great post at Learn~Play~Imagine on how to make oobleck (all you need is cornstarch and water!) with lots of variations and ways to play with it.
Kids will love this idea at Mama.Papa.Bubba. for making playdough kits for their friends. Match the playdough colors and toy props to the child's interest and you've got a hit for a homemade present.
Salt dough forms the base for these glittery heart sun catchers at Homegrown Friends and the kaleidoscope centers are made from melted beads. Such a pretty Valentine ornament, gift, or party favor.