I found the Chicka Chicka Boom Boom and Chicka Chicka 123 songs on Youtube, and my 2 1/2 year-old would watch them forever. She even learned which button to click to play the video again. But I wasn't comfortable letting her loose on Youtube, and I didn't want to be sitting there next to her, stuck watching these over and over again either, so I decided to buy them on DVD.
I couldn't tell you if any of the other stories are any good, as she's not interested in seeing them yet. She insists we put the DVD on the menu screen and she chooses whichever Chicka Chicka song is in the disc drive (she watches on a computer) and clicks the image from the menu to watch over and over (and over and over) again. She even tries singing the songs as she jumps around on the neighbor's trampoline!
I don't think these stories teach her numbers or letters, really. For that, try the Leapfrog DVD series. They've done wonders for her letter/number recognition and phonics! In the Chicka Chicka stories, the letters and numbers move too fast on the screen, and the lyrics whip by so fast, plus some of the figures are altered to have hair or be injured, or whatever, so they don't even look right. But these are great for reinforcing and remembering once they've basically learned their letters and numbers, and the tunes are catchy and a lot of fun.