There's not an awful lot to be gleaning right now, at least in the northeast, but we'll be in the thick of things soon. 
Gleaning is a process, dating to biblical times, in which leftover crops are collected or harvested after the farmer has  commercially harvested a field or orchard. And Wikipedia notes that "In Nineteenth century England gleaning was a legal right for cottagers. In a small village the sexton would often ring a church bell at eight o'clock in the morning and again at seven in the evening to tell the gleaners when to begin and end work."
Interested concept, eh, Greenhorns?
Here are some resources for gleaning America's fields:

• The Mid-Atlantic Gleaning Network (MAGNET)
• Society of St. Andrew, VA
• Salvation Farms Gleaning Network, VT
• The Gleaning Network of Texas