This is one of those nifty little resources that has actually worked for all of my kids I've tried it with (I bought our copy when Terri, now 9, was 3 or 4 years old).
Many people are familiar with Montessori-style sandpaper letters to help children learn the alphabet in a multi-sensory fashion. Children look at the letter, trace it with their finger and say the sound of the letter at the same time. It works, but some children (particularly those who are sensitive to texture) find the rough sandpaper feel very irritating. Besides, the set of sandpaper letters on wooden backings are quite expensive to buy (and a bit of trouble to make). Enter, The Red Letter Alphabet Book. It's a heavy cardstock, comb-bound book with a felt-textured letter on each page. The opposite page has black and white images of objects whose names contain the sound of the letter (you can also buy these images on cards to do related word games).
We've used this book quite casually with each of the children as soon as they were interested in it. We reached this stage with Frank just yesterday. Frank, proving Montessori's maxim of "work" having a "normalizing" effect, was wigged out over something out of our control (can't remember exactly what) and was completely miserable. I knew that this wasn't an occasion for discipline, but for distraction. The Red Letter Alphabet Book was handy and, on a whim, I brought it to him. Within seconds, and without any convincing needed, he was having me trace his index finger over the letters, his face locked in open-mouthed bliss (what a contrast from a few moments before!). He made me do it three times straight through with him right then and there.
These are available from Montessori Services. The same company also makes a Blue Number Counting Book which has also played an important role in our family's learning. I particularly remember Terri first using this book and, basically, falling in love with numbers right then and there. It was partly a matter of introducing this concept at just the right time for her, but I'm very grateful for these simple and gentle books for little ones.