The country's number one export is the black pearl, most of which are produced at Manihiki and Penrhyn atolls in the Northern Group. You'll be offered pearls at small shops and even by street vendors, but stick to dealers who are members of the local Pearl Guild, including those I recommend below. By and large, you will pay less for loose and set black pearls here than in French Polynesia.
There is a fine assortment of handicrafts to choose from. Particularly good if not inexpensive are the delicately woven rito (white straw hats), which the women wear to church on Sunday, and the Samoan-style straw mats from Pukapuka in the Northern Group. Carvings from wood are plentiful, as is jewelry made from shell, mother-of-pearl, and pink coral. The most popular woodcarvings are small totems that represent the exhibitionist Tangaroa; they might not be appropriate for the coffee table.
Rarotonga is one of the region's best places for tropical clothing, especially cotton pareus, shirts, blouses, and dresses. Some of the works are more artistically creative than those in French Polynesia, especially one-of-a-kind pareus and women's apparel.
For years the Cook Islands government has earned revenue from the sale of its stamps to collectors and dealers overseas. The Philatelic Bureau, next to Cook Islands Post, at the traffic circle in Avarua, issues between three and six new stamps each year. All are highly artistic and feature birds, shells, fish, flowers, and historical events and people, including the British royal family.
I recommend some of the best stores, but you'll find many more in Avarua.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.