There are about 5 Climbing Rock in Nepal that are cleaned and have pitons -- ready to use. The most popular is Nagarjun (just outside of Kathmandu) where most training happens. It is also the training grounds for Nepali Army Special Forces (where they learn to climb and repel).
Nagarjun -- Just outside of Kathmandu in the Nagarjun Forest, this is a great place to climb. There are 20 routes of varying difficulty, chimney climbs, overhangs and bouldering. The highest pitch is about 20 meters. This area is controlled by the army, and you must take a Nepali guide with you. Entrance fee is 250npr. Grades 4a - 7a
Hattiban -- About a one and half hour drive from Kathmandu, this is a really technical rock and quite challenging. You have to hike about 20 minutes into the forest from the road to get to the rock. There is camping, etc. nearby.
Kakani -- also about one and half hours from Kathmandu, there is only one small rock here with about 5 routes. But the mountaineering training grounds are nearby and there are really nice camping facilities. This is on some of the KTM valley trekking routes.
Thame -- This rock is near Mt. Everest and is at 3800 meters. It is a great training rock for those who are doing peak climbing or trekking in the area. There are 17 routes starting from grade 4c to 7c. This rock is multi pitch and about 200m high.
Bimal Nagar -- this rock is about 60km from Pokhara. It is just a five minute walk from the road. There are 5 fixed routes, but many other climbable routes for experienced climbers. This is a 4 pitch rock, and highest is 55 meters