Treks according to different regions of Indian Himalayas.

Darjeeling & Kalimpong Treks
Treks which are in Darjeeling and Kalimpong districts of West Bengal.

Garhwal Treks
Trekking trails which go through the Garhwal division of Uttarakhand. Garhwal, the westerly administrative division of Uttarakhand and lies in the centre of Indian Himalaya.
This area is divided into four major parts, Northern valleys, Nanda Devi Sanctuary, Central Garhwal and Western Garhwal.
Major peaks in this area are Nanda Devi, Kamet, Mukut Parbat, Mana, Trisul, Nilkanth, Chaukhamba, Shivling, Satopanth, Thalaysagar, Gangotri and Banderpunch.
Major trekking routes in Garhwal Himalayas are following alphabetically:

Kumaon Treks
Kumaun (also spelled as Kumaon) is one of the two Administrative divisions (the other being Garhwal) and the eastern part of Uttarakhand that lies to the west of Nepal.
This region was once popular for trekking and mountaineering but taken backstage at present. However the area offers some of India’s finest and less-explored Himalayan treks. Thanks to its dense lush forests, charming meadows (Bugyals), very remote villages and majestic mountain views.
Major peaks defining Kumaon’s trekking landscapes include Nanda Devi Main & East, Panchachuli group, Nanda Kot, Rajrambha, Api-Nampa, and several peaks around Pindari and Sunderdhunga valleys including Maiktoli and Panwali Dwar.
Major trekking & Mountaineering hub: Munsyaryi/Pithoragrh and Bageshwar.
The area is majorly divided in three valleys:
1) Darma Valley – The eastern flank bordering Nepal. Dharchula town is the gateway for the part.
2) Milam Valley –
3) Pindari and Sunderdhunga Valley

Sikkim Treks
Treks which are in Sikkim, Eastern Himalayas. The Indian state of Sikkim shares a mountainous border with Nepal in the west, Tibet/China to its north and east, and West Bengal to its south.
High mountains, passes and glaciers are located in the northern and western part of Sikkim and thus they are the main attraction areas for the trekkers and climbers.
Kanchenjunga, Kabru group, Pandim, Tent Peak, Forked Peak, Siniolchu, Sugar Loaf, Pauhunri are few amongst the high Himalayan peaks.