Something dd and I immensely enjoy is when I toss her up in the air.
I've done this as soon as I felt she was ready (at 4 or 5 months? I don't remember). Just a little bit at first, and I always checked her facial expression to see if she was comfortable with it. Over time, she enjoyed her little flights so much that I started throwing her up with all my power. I love her big smiles when she's up in the air. We really need to take a picture of that!
I can toss her up comfortably around 10 - 15 times before my arms get tired (dd is over 20 pounds now). Besindes being fun it's a really good shoulder workout, too!