As well as offering unique excellent accommodation in the center of the city, High Street Hostel stands out for being the most eco-friendly hostel in Edinburgh.
http://www.hostelbookers.com/hostels/scotland/edinburgh/3…

It has all the facilities that you might need during your stay – kitchen, Wi-Fi, 24 hour reception, laundry, games room – and you can use them without leaving a carbon footprint.
The hostel own a 75+ hectare of woodland that offsets more than the CO2 emissions from fuel they consume. In addition, all their electricity is sourced from renewable non-nuclear supplies and as many materials as possible are recycled – meaning at the High Street Hostel you can enjoy a trip to Edinburgh without making an impact on the environment.

If you are looking for something cheap and clean to stay for the night (or some more), you are at a good address there. It it simple but very clean, with 8-bed-rooms. You will meet very different kind of people there, very often for worker-holiday, also typical backpackers hostel. No kids. An open kittchen, if you want, you can cook there on a huge gas-oven, store your food in community-fridges and labeled boxes. You can also buy breakfast (and as I remember right, they cook every day at a certain time). Cleaning every day, open 24h, very central in the old town, few minutes away from the castle. In the community room you can read, play billard, listen to music, talk and watch a film every night for free.
Nice place to be.