For the more hard-core outdoorsy folks, you can hike the multi-day 26-mile Inca Trail covering mountain, cloud-forest, sub-tropical jungle, Inca paving stones, ruins, and tunnels. It's quite an experience, but reservations typically need to be made up to 6 months (or more) in advance given that permits are only issued for 200 trekkers a day.
You can also look into one-day hikes to Huayna Picchu (as long as you book at least 2-3 days in advance or get up extremely early as it's restricted to 400 people/day) which allows you to hike to the peak that looks down on Machu Picchu.
We did the simple one-day tour (thank goodness due to my altitude sickness!) with a 5:30am pickup from Cusco and a 6:20am Vistadome Train to Aguas Calientes, the base of where you catch half-hour buses to Machu Picchu. Orignally debating between the Backpacker train or the Vistadome Train, we were glad the former seats were sold out! With the comfy seats and breakfast and snacks of pancakes, grapes, jam, quiche, etc., the 3.5 hour train ride was a perfect experience with Vistadome. There is also an infamous fashion show by the staff of the train on the evening returns which is quite an entertaining experience in itself!
Note: Don't be so preoccupied with photos that you leave your bag (with passport, money, and return train tickets!) at the Temple of the Sun like me. You'll likely get it back as the security at Machu Picchu is quite good, but it'll be a stressful situation.
Rise and shine on the Vistadome Train!
Machu Picchu it all its glory. Check off the life to-see list! :)