These are some links I have found to be informative and useful:

Yosemite Online
This is a multipurpose web site dealing with many things “Yosemite.” It is a labor of love by Dan Anderson, long time Yosemite enthusiast. It is broken up into a number of sections and interlinked. I find the Yosemite Online Library the most interesting. There is also the FAQ and some online “exhibits” such as a discussion of how the valley was formed.

National Park Service
For Yosemite. Like all of the National Parks sites, this provides specific details about what is current with the park.

Restore Hetch Hetchy
Hetch Hetchy Valley was flooded to create the Hetch Hetchy Reservoir primarily for San Francisco and its water and power needs. This was done by an act of congress signed in 1913, while Hetch Hetchy Valley was part of the National Park Service and while the park service itself was in its infancy and was unable to effectively lobby against it.

The goal of Restore Hetch Hetchy is to reverse that:

The mission of Restore Hetch Hetchy is to return the Hetch Hetchy Valley in Yosemite National Park to its natural splendor ─ while continuing to meet the water and power needs of all communities that depend on the Tuolumne River.

The site offers its plan to do just that – it creates a blog keeping those curious or concerned informed – it provides videos, documents, history – it’s a veritable go-to site for all things about the restoration and the organization’s current projects.

Sierra Club
This organization was founded in 1892 by John Muir who acted as its first president to help insure the pristine and valuable wilderness in the Sierra Nevada mountain range. It has grown to a membership well over 2 million strong and has expanded its concern to include protection of the air, water, animals and the environment in general.

All Trails
This is a digital network that provides individual assistance in finding recreational venues near your residence.