OER.Directory is explicitly that; a directory of CC BY 4.0 open educational resources for gen-ed college courses.
Most students don't know these free textbooks exist, at this scale. Most professors know one or two sources but not the full landscape. There's no single place that organizes all of them.
Why doesn't a resource like this exist?
So I built one.
Working full-time in procurement at a tier-1 automotive supplier and pursuing my degree in operations and supply chain management; I built this because I needed it. The classes I wanted to take, wouldn't count as a transfer credit. Being hungry for knowledge and chasing rabbit holes; I sourced every single class that I wanted to take.
The free textbooks were out there but scattered across a dozen platforms with no central directory. I used the same lean methodologies from the plant floor: root cause analysis, process mapping, systematic verification; to solve a gap that shouldn't exist.
Every source listed here is CC BY 4.0 licensed; verified, not assumed. If it's on this site, you can verify it yourself; the source link is right there.
Direct, no fluff.
— Neal Widener