If you see that an infant is making a lot of noise for fun (such as banging a spoon against a plate), you can tailor an activity to his interest in his sense of hearing. If you notice him banging things against each other at lunch, set up a "drum" set with a spoon and pots, pans and other items he can hit to make different tones and volumes. This will encourage him to experiment with his sense of hearing in a creative way.
Infants also tend to explore their sense of touch. For example, an infant may become fascinated with the way a window feels against her fingers, insisting on being near it and touching it over and over again. To encourage her to experiment with her sense of touch, set up a variety of textures and let her sit among them and touch them. Tape, Velcro, paper and cardboard are good examples. Old clothing is also fun, because it comes in a variety of textures.
A cardboard box is a fun, creative activity for infants. Put it on its side and let infants crawl in and around it. Its textures and the fact that they cannot go through the box will be fun for them and encourage low-level problem-solving skills.
Dancing is fun, though very young infants tend to prefer slower swaying rather than more energetic dancing. Once babies are 3 to 6 months old, though, they may enjoy being swung up in the air or being held while you spin around. You can get creative with your moves, too -- babies don't mind if you have poor timing or odd-looking moves.
Singing is fun for babies too. Sing little songs like "Old MacDonald," but creatively change them to make them more personal for the infant, using his name or his favorite animals.