The US Open is always a youngster-friendly affair, and particularly so on Kids' Day. The event, which honors the humanitarian legacy of '68 US Open champ Arthur Ashe, features live music, interactive games, plenty of tennis instruction and chances for kids to play against each other and against touring pros, and appearances by top tennis stars and pop stars side by side. Past participants have included Carly Rae Jepsen, Rihanna, Justin Bieber and Will Ferrell, as well as Rafael Nadal, Andy Roddick and Kim Clijsters. Tickets are relatively inexpensive—cheap enough for budding fans to pay for out of their own allowance. For more information, arthurashekidsday.com.