AdSense recently introduced a feature called video units, that lets you include relevant YouTube video on your blog, and make money from ads on it. Here’s what they have to say about it:
“We’re excited about the launch of video units — a new way to enrich your blog with quality, relevant video content in an embedded, customizable player. Simply embed a snippet of code and have relevant YouTube partner content streamed to your blog. You can choose categories of video to target to your site, select content from individual YouTube partners, or have video automatically targeted to your blog’s content. Companion and text overlay ads are relevant and non-intrusive. To further blend the YouTube player into your blog, you can also customize the color scheme and layout as well as choose from three different player sizes.”
AdSense Help has some more information about video units. Once you’ve created the code for a video unit, you can easily add it to your blog’s template using an HTML/JavaScript page element.