A nifty web-based (with desktop option) writing tool that helps you edit by identifying sentences that may be hard to read. Also identifies use of adverbs, passive voice and words that can by simplified.
A group of creative-commons & copyright-free images from Miami University Libraries' Digital Collection. Includes historical images that range from MU to the Gutenberg Bible.
A fast and simple document collaboration service. Start a document and share the link. Good for "quick" collaborations where the text will be copied and pasted into a more permanent location.
Vellum is a free app to create eBooks. Supports cross-platform output. But, they charge you to export your eBook. Still, looks like a pretty friendly tool.