These are primarily resources that have public domain texts. Not everything on these sites is in the public domain, so pay attention to dates and copyright notices. I've tried to leave out resources that provide free access, but not necessarily public domain materials. As always, please do your own research before reusing content you find online.
See the Finding Creative Commons content page for text content that is licensed for reuse.
This work is licensed under a Creative Commons Attribution-NonCommercial 2.0 Generic License.