Home Depot, Lowes, Urban Outfitters. If you Google it you'll see that someone put together a list.
Be careful at the parks. Children will do unpredictable and (to the dog) threatening-looking things, like running up screaming with excitement. YOU have to anticipate this and prevent it, while still communicating a relaxed vibe to the dog.
Also, 90% of the parents there understand and like dogs and don't mind if their kids approach. The other 10% will call the police to report you in violation of the "no-pets-on-these-premises" ordinances. You know the type. If someone casts you a dirty look, it is IMHO better to relocate, and live to fight another day.
We still go to these places and get great socialization--just remember to be aware at all times of what is "about to happen" to make it a successful outing.
Liesl, b. 1/1/11