Kiteboarding Zanzibar is IKO certified and equipped with modern kit. Its Nungwi base is linked to its centre at Pwani Mchangani (where clients are taken if conditions aren't good at Nungwi). If you know what you're doing, and have certification, you can rent gear. For everyone else, lessons are available.
It's located on Nungwi's west beach about 100m north of Paradise Beach Bungalows.