The Center for the Study of Adult Literacy contains plenty of resources around this topic on their website. In addition to the general resources, they have a library containing 1,600 web-based readings that are organized into the three categories of Easier, Medium, and Harder to help access topics such as jobs, money, health, social studies, sciences, and other life skills. All have been reviewed to make sure they are the proper reading level.
Click here to view their website: http://sites.gsu.edu/csal/
Click here to view their library: http://sites.gsu.edu/csal/library/
The Times in Plain English is a site that converts news articles to a lower literacy with simple organization that would do best for advanced beginners and English language learners. They pull from a variety of newspapers including the New York Times.
Click here for more information: https://www.thetimesinplainenglish.com/
Southwest Adult Basic Education has a mission to provide adults with educational opportunities to acquire and improve their literacy skills necessary to be self-sufficient and to participate effectively as productive workers, family members, and citizens.
Click here for more information: https://www.southwestabe.org/
Reading Skills for Today’s Adults contains stories by reading level, along with the audio versions of the stories, questions for determining reading comprehension, and links to print PDF versions of the stories and questions for offline use.
Click here for more information: https://www.readingskills4today.com/
Reading Skills for Healthcare Workers contains stories geared around healthcare and medical information. While it is likely aimed towards non-native English speakers, it makes a wonderful resource for native English speakers as well.
Click here for more information: https://www.reading4healthcareworkers.com/
Learning Chocolate is a vocabulary builder tool aimed for younger readers, but has application towards beginning adult readers too. It organizes words thematically with illustrations and audio links for every word, along with basic online activities and games to help increase comprehension.
Click here for more information: https://www.learningchocolate.com/