Some Open Access publishers have questionable reputations and credentials and often charge authors to publish with their journals. A list of questionable journals can be found here. Please research the reputation of any journal carefully before submitting your article.
Open educational resources are resources that are free to use for educational purposes. The amount of educational material is growing every day. Below are some links to sources for use in your classroom. If you can't find what your looking for contact the Copyright Office for assistance in locating materials.