PlagTracker - Plagiarism Checker
Highlights sentences, shows links to sources where content came from. I wish it showed the original and copied content side by side so it was easier to compare; you have to just go to the source and find it yourself.
Rewordify.com | Understand what you read
Paste difficult to understand text into the yellow text box, and this website will give you a simplified version. While this is intended for people learning English vocabulary (or teachers helping students), it might be helpful as an instructional designer. It doesn't do anything for absurdly long sentences (in fact, sometimes the simplified version is longer), but you could use this to take a first pass edit on complex SME language.