* Plant a vegetable garden in your FRONT yard, and put a picnic table smack dab in the middle. The idea is that passers-by will stop to snack, help harvest, or dream up a potluck with the bounty
* If your backyard neighbor is a friend and is willing, take down the back fence and share your backyards - or make a shared backyard retreat in one corner surrounded by plants and comfy chairs - or at the very least create a little walking path from door to door so you can borrow a cup of sugar more easily (this opens up a whole street to you!)
* Build a register of neighborhood tools and equipment (such as lawnmowers, clippers, hammers, saws) that neighbors are willing to share. Operate it as a library so you'll be able to keep track of who has what checked out at any given time so the next person who needs something will know where to go look.
* my favorite: Somewhere near the street, place a little covered/waterproof box on a pole at eye level (i.e. something like an extra mailbox) for a book and magazine exchange. When someone walks by, they can take one, leave one at will. Great way to share books you love or magazines that might be of interest to someone else before they're recycled.
Of course these ideas will only work if your neighbors are kind and like-minded enough not to sneer at you for even proposing such things. I do think there are plenty of places that are ripe for this. I'd love to hear from anybody that has other ideas OR anybody who is already doing some of these. Let me know.