Aztec includes Foundations, Fundamentals, and Bridge, Ready Work, and Lifeskills (Corrections Reentry), as well as Kaplan. Their Continuum of Learning is a series of computer-based, instructional programs that provide diagnostic and personalized learning experiences, with a focus on core academic subject areas for adult learners.
Khan Academy, modeled after computer gaming, uses YouTube videos to cover a wide range of subjects, including math, science, computer programming, history, art history, economics, and more.
MyOpenMath is an online course management and assessment system for mathematics and other quantitative fields, focusing on providing rich algorithmically generated assessment to support the use of free, open textbooks like the ones listed on OpenTextBookStore.com. MyOpenMath is a collaborative community of users.
Readworks.org provides a high-quality library of fiction and nonfiction passages that can increase reading comprehension (both literal and inferential), vocabulary acquisition and writing skills for learners. It is targeted at K-12 grade readers, but is easily transferable to adult learners.