Plaza de Armas
Walk around the Plaza de Armas; the square has churches, shops, restaurants and bars backing on to it and is a great place to spend an afternoon. The historical center of Cuzco is beautiful, but you will have to deal with all the street vendors and hawkers of cheap paintings and other souvenirs. They are everywhere in and around the Plaza de Armas. They somewhat spoil the experience.
ProPeru
A great program for students and part of the ngo proworld service corps. they do sustainable community development work such as building kindergartens, irrigation systems, and fish farms in rural communities in the sacred valley. they offer semester programs, internship programs, and short-term group programs, all ranging from a few weeks to a few months. programs include living with a host family, sightseeing, spanish classes and other coursework.
Sacred Valley communities
For the adventurous, communities in the sacred valley often welcome volunteers to teach english or provide other skills to community members.
Bruce Peru
In the city, there are many opportunities to work with street children. the most notable is called bruce peru. there are also opportunities to volunteer at one of the cities' orphanages.
Sapo,
Play Sapo, a traditional bar game played in chicharias all over Peru. The game involves throwing small coins, called fichas, at a table with a bronze sapo toad attached. You get points for making it into holes on the table, and a ton of points for making it into the sapo's mouth. Best played while drinking chicha corn beer at a local dive. Ask old men to show you the correct throwing form, as it's difficult to master.
cuy,
Talk to local store owners, curators, waitresses and bartenders. They typically know a little English if your Spanish is not good, and are generally happy to share interesting information about the city not found in guidebooks. This is also a great way to find the best places to try cuy, alpaca, and chicha.
Rent a motorcycle
There are several shops on calle plateros, just north of plaza de armas, that rent motorcycles for the day. you do not even need a motorcycle license, simply any kind of driving license from your home country. prices are typically $40/day which includes two helmets, gloves, and jacket. sacred valley moto tours, at calle plateros #399 corner of siete cuartones, has new bikes in good condition. where to go? a loop of the sacred valley, taking in the market at pisac, lunch in urubamba, and several incan sites, can easily be done in one afternoon. or head south to some of the less-visited but just as pretty small towns and inca ruins.
Mountain Bike Tours
Downhill Mountain Bike Tours are available either across the Chincheros plains, past Inca ruins and down through the spectacular Maras Salineras or the 75km downhill from Abra Malaga to Santa Maria and onto the totally awesome hot springs of Santa Teresa and easy and cheap access to Machu Picchu from here too. Again go with the experts as there are a lot of cheap bikes out there totally not up to the job.