readworks has a zillion free reading passages available for download and in many subjects.

They come with comprehension questions, but I wouldn’t use them. The passages themselves, however, are rated by reading level, and could be very useful for English Language Learners – particularly in Social Studies. I could use them with students to help them develop knowledge preceding their beginning a more complex text on the same topic, or use them to supplement content in our ELL history books. It would also be easy to modify their reading passages into clozes or other reading exercises.

I’d say their content is similar to what you could find on Edhelper, which I’ve used for years to get passages to use for similar purposes. One key difference is that ReadWorks is free, while Edhelper charges (a small amount).