Yes. There is a wealth of material out there which is either in the public domain (meaning copyright has expired) or available under Creative Commons licensing, which generally means the work is available for free, subject to certain limited conditions, such as non-commercial use only and acknowledgment of the author. This includes open access publications, which generally use Creative Commons licenses.
For Creative Commons materials, visit the Creative Commons website for more information and check out their content directories which list audio, video, image and text materials available under Creative Commons licensing, or search using their Search page. To find open access materials, start with the Copyright Resources and Links for Instructors page.
For public domain material, simply search online for ‘public domain’ and the type of material you’re interested in. Some useful sites include: Project Gutenberg (the largest collection of copyright-free books online) and Wikipedia, which has an entire page dedicated to public domain resources.