ABCKids 1 is a nicely designed beginner app that introduces the alphabet and numbers. This app is normally $0.99, but it is available for free download for a limited time. This app is well worth the paid app price.
I really like the wooden puzzle motif which lends a bit of naturalness to the app. There are eight activities in the app. There is a flashcard activity which introduces the letters and numbers with animals and spelling. There are also toddler friendly puzzles, memory and shape recognition activities for the alphabet and numbers.
Recommended for ages 18 months to 3 years.