Just finished writing an article about Wide-Open Sandboxing called "The Dam War" for Adventure Quarterly #4.
Here is a sneak peak
"I created this article for Game Masters that want a wide-open sandbox campaign without the risk of Player Characters getting lost. In a wide-open sandbox you are not going to know what the ultimate outcome of the campaign is going to be so you will need use a higher level of improvisation than a typical adventure. Instead of a railroad or amusement park of encounters, GMs will need to design one detailed encounter to provide the hook introducing the PCs to a series of Non-Player Character relationships and encounters triggered by the actions of the PCs. After the initial encounter, these character relationships and action drive the plot. The important part of these NPCs is each one needs to have its own agenda, the want something from someone else, and that these agendas conflict with the agendas of other NPCs."