Adventure Specialists (U.S. tel. 719/783-2076, www.adventurespecialists.org [1], prices vary, call ahead) leads highly recommended, custom horse-packing trips all over Peru and especially in the Cusco [2] area. Founder and co-owner Gary Ziegler is a true adventurer, archaeologist, and noted Inca expert.
Manu Expeditions (Pardo 895, tel. 084/22-6671, www.manu [3] expeditions.com, prices vary, call ahead) offers a range of horse-riding expeditions that explore areas of the Vilcabamba and Choquequirao (17 days), as well as Machu Picchu [4] and the surrounding cloud forest (15 days). Another of its itineraries is from the Andes to the Amazon (14 days). One- and two-day rides around Cusco are also offered.
The best options for riding Peruvian paso horses is Wayra (part of the Sol y Luna Hotel outside Urubamba, tel. 084/20-1620, info [at] wayrasacredvalley [dot] com, www.wayrasacredvalley.com [5], US$195 per day) and Perol Chico (Carretera Urubamba–Ollantaytambo, tel. 084/974-79-8890, www.perolchico.com [6], prices vary, call ahead).
Links:
[1] http://www.adventurespecialists.org
[2] http://www.moon.com/destinations/peru/cusco
[3] http://www.manu
[4] http://www.moon.com/destinations/peru/machu-picchu
[5] http://www.wayrasacredvalley.com
[6] http://www.perolchico.com