Communities thrive on the talents of their members...consider what you have to offer and find ways to bring that into your community.
Anything we do on a small level will automatically ripple out into the larger system. If you have a special gift when it comes to bringing people together...find ways to bring that into your community.
You might agree to throw a party or event once a year that includes the whole community. Even a small open house in an apartment building can accomplish a lot in terms of making people feel more connected and comfortable with each other.