Charity Navigator (https://www.charitynavigator.org/) can be used to research these organizations.
American Whitewater: https://www.americanwhitewater.org
The Stewardship News on The Stewardship Page lists a number of ongoing projects and issues including when public comment periods open. There is also a link to ‘Regional Projects’ page. Search on “(CO)” to find projects for Colorado. Where comments are requested, they provide an on-line action link as well as talking points and other ways to submit comments. They recommend personalizing comments.
Outdoor Alliance: https://www.outdooralliance.org/
Outdoor Alliance is the only organization in the U.S. that unites the voices of outdoor enthusiasts to conserve public lands. We help ensure those lands are managed in a way that embraces the human-powered experience.
Southern Utah Wilderness Alliance: https://www.suwa.org/
The Southern Utah Wilderness Alliance (SUWA) is made up of concerned citizens from Utah and throughout the nation who share the common goal of preserving Utah’s remaining desert wild lands, known collectively as America’s redrock wilderness. You can sign up to get text message alerts and has an on-line action link to submit comments.