Himachal Pradesh Trekking Information
Himachal Pradesh is another of India's major trekking destinations however there is none of the lodge infrastructure that exists in neighboring Uttarakhand so most treks are camping only. There are a few homestay trekking options in the Spiti Valley. I have done a few treks in Himachal but not as many as Ladakh or Uttarakhand in addition to the treks I've done I mention a few of the other popular treks in the state.
Best Season: May-September (Spiti Valley), April-May and September-October (all other areas)
Base Cities: Manali (Bus service from Delhi), Dharmsala (Bus service from Delhi), Kaza (Bus service from Manali), Kalpa (Bus Service via Peo from Shimla and Kaza)
Guide book/Maps: Lonely Planet Trekking in the Indian Himalaya
A few other options for trekking in Himachal Pradesh that I have not done yet personally but are certainly good options in the region:
Indrahar Pass This short trek is probably the most popular trek from Mcleodganj, near Dharamsala. To go to the Pass and back takes about 3-4 days. It may be possible to do this trek without a tent making use of the rest house at Triund 10 km from Mcleodganj and doing a long day trek to the 4316 m Indrahar pass. It is also possible to continue over the pass to Kharamukh (5-6 days).
Kaza to Dhankar Gompa I've heard its possible to trek between Kaza and Dhankar Gompa via the high plateau to the north of the valley staying at homestays in the villages along the way but I do not know the details. It should take about 2-4 days.
Pin Valley to Kinnaur This trek links the Pin Valley to Kinnaur taking about 5-7 days to complete and requires camping equipment and food. An interline permit is also required which you can get easily in Kaza free of charge.
Trekking Practicalities :
Fortunately there is little regulation of trekking in Himachal and for the most part you are free to go where you wish. Exceptions are treks that pass through the areas close to the Chinese border. For these treks you will need an interline permit usually pretty easily obtained for free from the nearest major town. In the past there have been incidents of trekkers being attacked and robbed in the areas around Manali and the Pravati Valley and most guidebooks discourage independent trekking in those areas. I'm undecided as to whether this is justified or not. More than likely you would be fine but it is undeniable that there have been some incidents in the past so it is important to weigh the risks before heading out. But remember it always "feels" safe until something happens.