Creative Playhouse: Sand Playdough. Mix sand into playdough (or brown sugar if you don't have sand) and play with shells. Great sensory play, beach themed idea.
Make your own playdough
Montessori Monday - Montessori-Inspired Spring Playdough Activities (roundup post with ideas for a number of springtime themes)
Dough made with hair conditioner and corn starch. "Think of this as a mix between playdough and cloud dough. It is light and airy like cloud dough, but moulds better as the conditioner helps the cornstarch become more pliable."