The Letter Factory because it is funny and very 'animated'. The others follow right along. They even have math videos. These have been around a long while and I realize that there are new fangle-dangled learning toys out there. My kids have tried most of them but really loved the videos the most.
You can order the whole beginning set from Amazon here.
We also did simple workbooks from the dollar stores and Walmart. I found that with my children the books with colorful pages got the best response. Kumon workbooks are awesome. Every night my oldest daughter went over the alphabet and numbers to twenty with flash cards. Sounds boring and repetitive, right? Well, that is just what we did instead of reading bedtime stories because we read stories all through the day. She was still sleeping with us and I had to find something to help her relax enough to go to sleep and I wanted to overachieve..don't judge- we all do it with our first borns:) Anyway, we did the flash cards each night, stories and poems during the day, and colored shapes in between.
I of course, didn't do the flash cards at night with the second daughter because...well, I wanted my bed and worked a little harder on teaching her to sleep in her own bed. But she is doing well. She didn't know all her letters and numbers at fifteen months but she did by eighteen months. So, no harm done.
I hope this helps a little. I'll go into more detail next week.