Nagarkot is a small resort village on the Kathmandu Valley fringe, and the best place to see Mount Everest without taking a trek. It's a great place for mountain views, especially at sunrise. There are several good walks around the area. There is a cheap minibus to the resort from Thamel.
Between October and March you are pretty much guaranteed good mountain views . During June to September you'll be lucky to get a glimpse through the monsoon clouds. It is much cooler in Nagarkot than Kathmandu, and in autumn and winter you'll need to wrap up well. The resort is a bit fragmented due to a proposed army camp that never developed.
You can get there one day, see the views and leave the next morning. To take in a walk spend another night or two.
Sights in Nagarkot
The only thing to see are the amazing views. Mount Everest is a dot on the horizon, but the other peaks of Dhaulagiri, Kanchenjunga, Ganesh Himal, Langtang Lirung, Shisha Pangma, Dorje Lakpa and Gauri Shankar are more impressive. There is a lookout tower reachable in an hours uphill walk that offers 360 degree views.
Activities in Nagarkot
Hiking is the only activity. A range of walks from 1 hour to 2 days are possible. The Lonely Planet Nepal has good descriptions and instructions of the walks.
Accommodation in Nagarkot
Nagarkot has a selection of guest houses and hotels, but quality is a little low, but most have great views. Most have a restaurant.
Getting to Nagarkot
In high-season there is a daily tourist minibus from Lekhhnath Marg (north of Thamel) at 13:30. It returns from Nagarkot at 10:00 from the Galaxy View Tower. It takes 2 hours and costs NRs325 one way. Tickets, including returns, can be bought at Wayfarers. Large packs can go on the roof.
It's possible to get a taxi from Kathmandu, but it'll cost NRs1400 one way. You can also walk.