Dave and Ava's slogan is "Rediscover Nursery Rhymes!" Compared to many of the other related cartoon series on YouTube, Dave and Ava is on the higher-quality side. The animation is excellent and the singing and music is generally top-notch. They have very long videos, too. While they repeat the same ones over and over again, it means you don't have to change the video for awhile. This seems to be the case with most of the nursery rhyme videos. But, Dave and Ava's are the ones that capture my daughter's attention the longest.
If you have a child ages 0-6 and you're looking for a good video series on YouTube for your child to watch, I'd definitely recommend this series. Dave and Ava also have a mobile app for Apple and Android, which you can subscribe to monthly or yearly. The app also features some other activities, as well. For ad-free entertainment that can last your child months or years, it's a good deal for Apple or Android device users.
Dave and Ava currently put out new videos regularly on YouTube.
If you know any other really good YouTube video series for kids, let us know in the comments!