I know videos and screens in general can get a lot of bad press but at the age of 24 months, my youngest had pretty much taught herself the alphabet and numbers to above 10, from being allowed to choose and enjoy preschool songs and materials, through such mediums.
Although not everyone may be a visual learner, for those that are, ICT, such as computers, tablets and videos, can be a great asset.
Some of my daughter's favorite videos can be found on the selection of video channels shown below. Her favorites are any which are related to the alphabet or numbers. She has recently progressed onto choosing to watch vidoes involving addition and word building (let me know if you'd like links to those please)! Other than monitoring and a bit guidance and supervision, I have to admit, I can't even take the credit for it!
I hope some of your young ones enjoy the videos too. If they like the Busy Beaver songs, there is a paid for them app here, however, the video channel links are free to use.
Preschool Learning Videos: EduBuzz kids; Kid's TV123; Kid's Camp; Baby Big Mouth.