There's an interesting book called "Native Reading" that gives some excellent ideas on ways to introduce babies and toddlers to books, reading, and letters in an age-appropriate manner (playing and reading aloud with the child on your lap, especially with one finger following under the words). This is FAR cheaper than the DVDs, but requires active parental involvement.
Keep it fun, make it special, keep doing reading and story time (even when they can read for themselves), point out letters, numbers and words all around them on street signs, in stores, on the boxes of toys or food that's in your cabinets. MAKE IT A GAME - and give them a lot of control in the games, that way you'll avoid the "learning burn-out" that one poster warned you about.
Toddlers LOVE post-it notes - one of our games is to write the name for something on the post-it and label things. (He sits on my lap and I'll say the letters as a spell out "M, O, M, Mom" and then he sticks it on me.) Another fun one is getting an index card that says "on" on one side and "off" on the other. And then I HAVE to turn the light "on" or "off" when he shows me the word. (I pretend that I'm trying to do something else like folding clothes and have to drop everything to hit the light switch when he commands, but he has to show me the right word and show it right side up. It's very slapstick and Three-Stooge-like and he just cracks up and has fun because he's pretending to be the boss. Be silly and improvise.
You'll learn to recognize their receptive moods and you'll also learn when they are NOT in the mood for those kinds of games. (I also get in the backseat with the kids and read to them almost everytime the whole family goes ANYWHERE. Adding 10-15 minutes of reading here and there really adds up.)
While pushing overly-academic material on kids when they care too young can have a detrimental effect, children who learn to read ON THEIR OWN TERMS at a young age have a great advantage because they can follow their own interests and entertain themselves at odd moments - riding in the backseat of the car, waiting at the doctors office, or all the times they are bored having to accompany adults shopping or doing errands, etc.
When he's older and starting to watch TV (certainly there's no hurry to do this, especially before age 2, but I'm assuming he eventually will), there are some fun DVD and CD sets about numbers, letters, and most recently science topics by the music group They Might Be Giants. "Here Come the ABCs" and "Here Come the 123s" and - you guessed it - "Here Comes Science". You can listen to the CDs in the car with the kids (and the music is actually enjoyable by adults, unlike 95% of kids music out there), and then you can watch the DVDs at home, and they are based on the same songs that they heard in the car.