My son is 3.5 and knows his alphabets well.
Now I want to tech him words, any suggestions on what videos / cartoons would be apt.
Of course I am talking about English.
Currently I am checking out LeapFrog video series.
Personally, I've found reading with children to be more effective than videos. Granted your personal time with your child may be limited, but it's arguably better and more fun for a small child to be reading with their parents than competitive games/sports where the parent has to compensate for their advantage.
If nothing else, you have the ability to pick up where he's struggling better than an automated system, and obviously you'll be vastly more interactive than a video.
With that said, Disney Sing-Alongs have the advantage of being repetitive, so he'll pick up the words of the chorus more easily, and the rhythm can help with memorization. Plus he'll be very cute.
You might look into Baby Einstein videos. These are often available from the library. Leap Frog has a good reputation. Sesame Street is an oldie but goodie. Nick Jr. has some good things too.
Also, this post mentions Word World videos.
There are some great apps for the iPhone. The ones we use are called Word Magic and Sight Words. Sight Words is customizable: you can record your own voice saying the words and add your own words in any language. These are good for kids a bit older.
My son (age 2) has really been into "Super Why". I think it is on PBS but we watch episodes online. It is a cute series where the four characters living in Storybook Village use their different abilities and the power of reading to solve problems. They look to books to find the answers they need. They spell, build words, zap words and replace them to change meaning, etc. It is pretty cute and the music is catchy too. One of my son's friends, who is 3, wears a cape and calls himself Super Why, so I know it can be interesting for older kiddos too.
I answered similarly in another question.
I strongly suggest watching the television with the Closed Captioning/Subtitles turned on. While it is not actively teaching vocabulary and reading; it is giving constant stimulus to show the words for the most part in synch with the sounds.
Our 4 1/2 is reading at probably a year or so ahead (with possibly the exception of attention span) as a result of having a deaf parent who requires the captions to be on.
The bonus is that it works stunningly well with children's programs but even with other random programming that might be on that you expose your children to. (We prefer How it's Made and Mythbusters. Our child recognised: Busted, Confirmed, etc)
Disclaimer: I agree with the other poster suggesting that reading time is more valuable than screen time. In my limited time as a new parent I have seen much support for that stance with respect to developing language skills and higher brain function in general.
Now, onto reality, where TV is going to be incoporated... My wife uses 'Your Baby Can Read'. from Amazon. Its a set of DVD's to watch with some heavy duty flash cards and other aids to get them going. The set is appropriate from 3months onwards, and we love it. Good luck!
There is evidence that video programs and television shows designed to teach children words actually reduce the vocabulary size of children who watch them. While often much loved by parents and seemingly by children as well, they are not more successful in teaching words than any video and they under-perform talking to, talking around, and reading with your child.
As I understand the brain and childhood development science, these types of videos should be thought of as entertainment not learning.
Please follow up on my answer with the following sources that helped form my opinion: