Can I use a Youtube video in my presentation for class?
You may usually use music, video, and images from public websites, like Youtube, in a face to face (F2F) lecture in a classroom. However, incorporating any media (including Youtube videos) into a fixed, tangible "presentation" or class site is less clear.
Pointing to or "embedding" publicly available media within Blackboard, PowerPoint, Prezi or other software is probably fine (unless there are licenses that, in fact, prohibit it-always read the fine print). However, capturing, downloading, or "ripping" media from those same public websites usually require your use to be evaluated as Fair Use, or be part of the exceptions provided by education exceptions in 110(1) and 110(2). If your use does not fall under Fair Use or 110 provisions you usually must obtain permission (again, unless there are licenses that permit it)
In all cases, it is best to document this use using a tool like the Fair Use Evaluator or the Exceptions for Instructors eTool. These provide documentation of "good faith" effort at responsible use and limit liability.
Additionally, JMU libraries has compiled a list of sites where you can find high quality media that may be used. Free Media for Creative Use offers audio, images, and video available under Creative Commons, Public Domain, or JMU license for you to use in your own creative endeavors.