The next town over from me has a fantastic soccer program, and it includes an under-four age group.
DD started around 2.5, and DS at 18 months, simply because I couldn't keep him off the field when his big sister was playing. They play in fall and spring for a few weeks, just like the bigger kids.
The under-four team is really excellent. Imagine 45 kids from 1 to 4 on the field, kicking soccer balls to their parents, playing red light green light with the coach, and generally having a chaoticly awesome introduction to soccer.
Every kid has his or her own ball to play with, and there is no actual game, but they are still learning introductory skills and getting practice dribbling the balls around. The coach is the most patient person I've ever met, I think. At the start of each practice he crouches down and the kids all gather around him and shout out little under-four factoids about their lives and their week, and he listens and comments on what they say before he starts the actual soccer portion of the day.
DS is just 4 and still with the little guys; DD is 5.5 and has moved up to the next level where they do play some little games. She loves that, too.
If this were a structured and competitive league, I wouldn't be a fan of it. The way it's set up, though, it's really comfortable for us. There is no focus on competition, and the soccer skills come naturally with the games the kids play. The coach applies no pressure at all, and I believe his own daughter refused to even try to kick the ball for most of last season. It didn't matter much to anyone; kids play if they want to and sit out if they'd rather.
