We're well on our way! :) I am going to lead out with a series of classes by Dr. Melissa West. There are TONS of them, so if you are interested in continuing with free online classes daily after the challenge is done, this would be an easy way to continue on with hour-ish long classes.
Here is the playlist where they can be found, if you are so inclined! :) She leans toward more beginner level stuff, so if you feel like you need more, seek elsewhere or buy a disc... but she's a good starting point for sure. :) This starts on page 3 of the list, so go to page 2 and 1 to see classes 2-100+.