Ahh, an age-old question! I've faced this problem myself, with a 4-year old and a one-year old. Luckily, my older boy loves board games, drawing, any kind of art project, reading and being read to, and working on his writing (he's learning to write all the letters in the alphabet). For my younger son, it's much more difficult. He's too young for art or for games. His favorite indoor activity is to take all the CDs off of our shelf and throw them on the floor of the den. When my older son was this age, we lived in a high-rise building that had an indoor playroom for children, a great diversion on a cold day and a good way to get him out of the apartment for a while. Unfortunately, we now live in a single-family house without such an amenity, though we do have a basement full of toys. Truth be told, I don't know exactly how we're going to do it this winter. Anyone else have suggestions?