It's not really clear just how many children suffer from one of the autism spectrum disorders (ASDs) -- some research suggests that as many as one out of every 150 kids may be autistic in some way. The National Institute of Neurological Disorders and Stroke says that between three and six of every 1,000 people have ASDs. There really is a spectrum of autism disorders, ranging from people who barely function or cannot interact with others at all to those who are high functioning and can learn to be well-integrated in social settings. It may be challenging to find fun activities for kids who have difficulty communicating and relating to others, as many ASD kids do; however there are games and play activities that can be both enjoyable and provide a positive learning experience for the children involved.
Autistic children often need help identifying and "translating" facial expressions. It can be both helpful and fun to have the child copy what you do with your face. The child tries to mimic your movements as you poke out your tongue or wrinkle your nose. You can make a variety of silly and funny faces for the child to mirror. In this way s/he is gaining experience in reading faces and interacting through expression.
Music speaks to people in a way that words sometimes cannot. High-functioning autistic kids may be interested in learning to read music and to play an instrument properly. Others may simply enjoy the repetition of drumming and keeping a rhythm in a positive social setting. Some autistic people are sensitive to particular sensory experiences; in this case, an instrument with a limited range of sounds and volume may be preferable. Singing, too, can help overcome some speech difficulties.