The main ruins outside Cuzco is Sacsaywan, Q’enqo, Pukapukara and Tambomachay, which can be visited in one day by yourself (the cheap option) or on a guided tour. To enter the sites (as well as a few more) a ticket called bolero turistico can be brought (costing in 2016) S130. Further afield in the Sacred Valley are Ollantaytambo, Salinas, Moray and Pisac,all of which are about 15km north of Cuzco. Driving between the isolated sights allows you to see a series of villages and snowy peaked moutains which are worth the long bumpy ride.
Expect a lot of tourist at the sites, unless visiting by yourself later on the day (which is what I did). Choosing to take the local buses is the harder option, and might involve a bit of waiting around for taxis to become full with other tourists, so if strapped for time travel agencies offer vans to do the loop at a price of about s70.
For many visitors the hike to do in Cuzco is Machu Picchu, but there are many more that are now on offer, to more remote places such as Rainbow Moutain (Vinicunca). From the pictures online, the1 day treck to 5200m would be worth it to see the 7 blended colours of red, yellow and blue lines covering the mountains. However the day we went a major snow storm hit the area, with a chance of causing the treck to be cancelled. But that didn’t stop us ( and the guide) to reach the peak. The treck isn’t easy and the peak is very cold (even if it doesn’t snow) so bring layers!