Non-textbook OERs are great resources to supplement lessons in order to meet outcomes/objectives. Here are a few sites that contain such materials as assignments, readings, lecture notes, presentations, educational videos, and more:
OER Global Search is a good attempt at a search engine specifically for OERs
OER Commons is a dynamic digital library an network. Explore open education resources and join our network of educators dedicated to curriculum improvement.
Portland Community College offers a large list of fully Open resources, courses, and repositories. These are also grouped by subject.
MERLOT is a curated collection of free and open online teaching, learning, and faculty development services contributed and used by an international education community.
Internet Archive is a non-profit library of millions of free books, movies, music, software, and more.
Project Gutenberg offers over 50,000 free ebooks: choose among free epub books, free kindle books, download them or read them online. Most works are available for free because their copyrights have expired.
Unglue.it is a project that crowd funds to pay to make books freely available to everyone around the world.