In order to visit the ruins of Cusco and the Sacred Valley any visitor needs the Boleto Turístico General which you can buy at the sites but also at the COSITUC (Comite de Servicios Integrados Turísticos Culturales del Cusco) in Av. Sol 103, office 102.
The ticket for 2009 costs 130 S/. which is around 44 USD/30 €. ISIC Student Visitor's Ticket costs 70 S/. (24 USD/17,5 €) and allows you to visit the following sites during 5 consecutive days:
The Contemporary Art Museum
The Regional Historic Museum
The Popular Art Museum
The Qoricancha on site Museum
The Santa Catalina Church
Inka Pachacuteq Tower
The Native Art nightly representations at the Centro Qosqo de Arte Nativo
Sacsayhuamán
Q'enko
Puka Pukara
Tambo Machay
Písac
Ollantaytambo
Chinchero
Tipón
Pikillaqta
Machu Picchu (124 S/. + train + bus + guide + ...)
The Cathedral on the Plaza de Armas (25 S/.)
Santo Domingo or Qoricancha (10 S/.)
La Compañía de Jesús, El Triunfo, La Sagrada Familia, La Merced and other churches
The Inca Museum at the Palacio del Almirante (10 S/.)
The Religious Art Museum (10 S/.)
The Stone with the 12 angles in Calle Hatun Rumiyoc (Free)
Barrio San Blas
San Cristóbal church next to Sacsayhuamán (Free on Sunday & holidays)
Colcampata Palace close to the San Cristóbal church
The bread capital of Peru: Oropesa - 20' by bus from Cusco
Sunrise at Tres Cruces near Paucartambo, only in June & July
American Sistine chapel in Andahuaylillas - 35' from Cusco
Maukallaqta & Puma Orqo (7 S/)
Antique tramway to Sacsayhuamán passing by lots of interesting buildings
Thermal baths in Yaurisque (on the road to Paruro & Maukallaqta)
Horeseback riding to Sacsayhuamán, Q'enko, Puka Pukara & Tambo Machay
Cycle in or to Lares Valley
Rent a mountain bike
Rent a motorbike (From Scooters to 650)
Quad tours
Rafting
Canoeing
Paragliding above the Sacred Valley
Hot air balloon flights above the Sacred Valley
Slingshot, bungee jumping or wallclimbing at Action Valley 11 km from Cusco
Sample some Novo Andina cuisine in the upmarket restaurants
try local specialities in off the beaten track eateries
Learn Spanish or Quechua at one of the several language schools
Go to local festivities
Try guinea pig at Tipón
Shaman experience
Massage & other medicinal plants therapies
Stroll around Laguna Huacarpay