Other Video Hosting Sites Beyond YouTube and TeacherTube

Currently preparing to flip parts of my class next year, I was bamboozled by the amount of video sites there are out there!  Where does one start?  Which ones are best?  How do you choose?

I am currently falling in love with Knowmia.  They boast that they have over 13,000 videos.  Not only can you host your own lessons, but you can browse the lessons of other teachers.  

They also have a How-To Guide on making lessons.  Also, they have a great, FREE, iPad app (which I plan on playing around with A LOT this summer).  Plus, in addition to the video aspect of it, you can build interactive assessments and track students' progress in real-time.  

Also, Teaching Channel is becoming more and more interesting to me.  It seems to be like Knowmia with more of a social media aspect to it.  You can find certain teachers who teach certain subjects and "follow" them.  

Plus, they have great professional development videos on how to teach with video.  (Videos about videos...meta, anyone?)

TeacherTube never really pulled me in, and YouTube is blocked for students at my school.  But these two sites may just be what I (and you) have been looking for.