I think the book "Sign Me Up!: The Parents' Complete Guide to Sports, Activities, Music Lessons, Dance Classes, and Other Extracurriculars" (2003) by Stacy M. DeBroff is good, giving an overview of many activities, including some you may not have thought of. Town recreation departments often have low-cost classes. Where we live their is a weekend school run by Chinese parents that offers (besides Chinese language) classes in contest math, creative writing, art, piano, chess, gymnastics, and fencing.