I am definitely biking up to 40th St & Camelback on Saturday night to check out the bats at sunset as they leave the flood control tunnel. This activity has been on my index cards for a while. Before or after I will hit either La Grande Orange for pizza or Il Postino for the awesome brushetta.
Also worth a look and a bargain at $2? The Banquet of Rocks at the Arizona Mining and Minerals Museum. Hit the Capitol Museum, the Pioneer Cemetery and the Grand Avenue shops and restaurants at the same time.