www.micahimages.com

Informational Forums (one of the best way to get current information on trekking is from active user forums)

http://www.indiamike.com/india/ (the best most well organized source of user generated information for travel in India including a trekking and mountaineering section)

http://www.lonelyplanet.com/thorntree/index.jspa (good source of information about budget travel covering the entire world)

http://www.yetizone.com/ (very good site on trekking in Nepal with forum and detailed online guides of treks in the Everest, Annapurna, and Langtang regions)

Online Maps

http://www.lib.utexas.edu/maps/ams/india/index.html?p=print (dated but detailed U502 map covering India and some of Nepal, one of the few maps you can find of the Indian Himalayas with contour lines)

Guidebooks

http://www.trailblazer-guides.com/books/ (best guidebook series for independent trekking the Himalayas unfortunately they only cover Ladakh, The Everest Region, and The Annapurna Region)

Mountain Health and AMS

http://www.ismmed.org/np_altitude_tutorial.htm (Good review with accurate and detailed information about the symptoms and treatments of AMS)

Trek & Tour Operators

While this guide is about independent trekking I recognize some people like the security and easy of an organized trek.  Below are a list of my friends websites who work in the travel industry all of whose  websites I have worked on myself.  I do not guarantee that they will provide the lowest price, but I do know all of them  very well personally and vouch for their character.

Nepal:

http://www.highaltitudedreams.com/ (Kili Sherpa- High Altitude Dreams, specializes in organizing 8000 m expeditions, including Mt. Everest Expeditions, as well as other climbing expeditions throughout the Himalayas, and high end treks in Nepal)

http://www.sherpa-adventure.com/ (Lhakpa Gyalzen Sherpa- Sherpa & Swiss Adventures, organizes treks, expeditions, and tours in Nepal)

http://www.himal-adventure.com/ (Phurba Gyaltzen Sherpa- Himalayan Sherpa Adventures, organizes treks, expeditions, and tours in Nepal)

India:

http://www.trekhimalayas.net/ (Mohan Nepal- Trek Himalayas, based in Sikkim, organizes treks and tours in Sikkim, Nepal, Ladakh, and Goa)

http://www.clickladakh.com/ (Showkat Ali- Indian Himalaya Expeditions, based in Leh, Ladakh, organizes treks and tours in Ladakh)