My DS is Feb '08 and I wouldn't have started him at this stage, however he has lots of LeapFrog gear that he has taught himself

The fridge magnet one helped him learn the alphabet song as he could sing it as many times as he wanted.
Then he can select a letter and it says "A says a, every letter makes a sound A says a" and we would say ... for 'apple' etc.
He also has a game that has taught him to write. I wouldn't have expected that in the slightest but he has taken a keen interest and can write many letters.
It has also helped him recognise numbers.
I feel like a slack as mummy for not having been able to teach him myself but i by no means thought he was ready.

At this stage I let him do it for fun, I do try to explain that we use the little letters most but he writes some in upper case and some in lower.
For example, he can't do an E in lower so he does it in upper case.

That said, he still can't really count to 10. And we have been practicing that for a loooooong time.