Upload a PDF and add video, images, audio, comments, and quizzes. (You can also annotate using a pen, but only you will see those annotations.) You can also create classes and add the PDFs and students to them.
Limitations: With the free account, you cannot make a document private.
Web app (and browser extension for Chrome) that lets you double-click any word to get a translation. It adds the words you click to a vocabulary list and quizzes you on them when you're ready. A wide variety of language available.
Simple online voice recorder. Share your recording via email or embed. Alternatively, you can upload a file. Recordings can be downloaded. No registration required.
Enter a text with special coding for annotations. The resulting text has clickable links that show the gloss in an area to the side of the text. You need to save the HTML page/code and put it into a webpage or LMS.