Vizia allows you to create markable online quizzes to accompany any YouTube video. Great for checking comprehension or highlighting key points. Collect responses in a Google Sheet and you can mark it using Flubaroo (Y/N, T/F, multiple choice only). Learn more in this posting at FreeTech4Teachers.
This is something I get asked about periodically. Here is a handy dandy video tour on just this topic, from FreeTech4Teachers.
Soundbible is an excellent source for free sound clips, sound bites and sound effects. No site registration required.