Most video sources these days are happy for you to embed their clips into your blog. Here are some (usual disclaimers included). A simple tutorial follows the list below. You might also want to use TubePrompter with these links.
how-to
All you have to do is copy the “embed” code at any of these links below (+ many others). The embed code is often seen in a text area near the “share” options and noted with icons like this:
All you have to do is copy the embed code – don’t even look at it – it’s too scary.