WatchKnowLearn is a great educational alternative to YouTube that hosts over 6,000 videos that are aligned to Common Core Standards.  If you become a registered user, then not only can you access these videos, but you can also upload your own.  Got a great lesson or presentation you want to share with other teachers or learners, upload it to WatchKnowLearn so that you always have access to it and others can benefit from your work.  You can also create your own classroom pages that contain a collection of videos you want your students to view.