Christina Tondevold, a.k.a. The Recovering Traditionalist, has released a free number sense video series!These will only be available through October 12th.
They are actually a part of a full online course Christina does all about Number Sense. So, people who register for the full course have access to all of them, plus many more videos (15 hours of instruction time). During the final video Christina will be talking about how you can register for that course if you are interested.
If not, she always re-releases these free videos each time she is about to open registration for the course. So, you could watch them when they get released again.