Machu Picchu Sanctuary Lodge
This superbly over-priced hotel is the only option for sleeping at the park. There are two equally expensive restaurants on site, and 2 suites that have partial views of the ruins. Unless you have more money than sense, you won't want to stay here. It's located just outside the ticket booth. Prices vary from 500 USD to over 900 USD per night, although it does includes all full 3 meals, internet and tv.
Due to the fact that this is a protected park, further construction in the area is nearly impossible. Thus, there is currently only one very expensive hotel at the site itself. Almost everyone who wants to overnight near Machu Picchu books a hotel in nearby Aguas Calientes.