An urban problem. An urban solution

I have a problem. A problem that I think links to urban sprawl. You see, I've moved within that past year, which is a common habit within the current patterns of urbanization. But to get straight to the point. My problem is that my social life has drastically changed. No longer can I knock on my next door neighbor's door and spontaneously start a pick-up soccer game, basketball game, baseball game, etc. Part of this is that my old childhood friends live further away or have become pre-occupied with adult-like responsibilities of work and post-secondary education. But, I feel that this is no excuse to no longer take part in the spontaneous acts of play. Hence, I ask 'how can I revive those spontaneous acts of play?' I understand that it isn't reasonable to expect everyone to be available to your spontaneous beckoning. This is why I propose that the internet can be utilized to mobilize and revive urban social life. More specifically, what I am alluding to is a 'Facebook-like' place where people can self-organize public activities and have the same old fun we had when we were children. Since our closest friends may no longer be readily available for a game of pick-up soccer, I feel that the internet (potentially linked with mobile phones) holds the potential to mobilize larger local groups of people who share same interests and desires of play. What I am calling for is help, ideas, a collaboration, to shape a space, a website, where we can overcome the social fragmentation of urban sprawl, and at the same time meet new people and form new communities. Part of this is a dream to revert back to the local scale of societal living.
PS: I've tried on Facebook, with a group called 'PLAY DAY,' but haven't been able to mobilize any real or concrete social engagement. Hence, I have been dreaming of an independent .COM site, separate from facebook, where non-facebook users could be incorporated.