Tree ID
Arbor Day's 'What Tree Is That':
Ohio Public Library's "What Tree is it":
LeafSnap Species:
Virginia Tech App: Virginia Tech Tree ID App

General Links
Arbor Day Foundation:
Alliance for Community Trees: 
Asian Longhorned Beetle:
Continental Dialogue on Non-Native Forest Insects & Diseases:
Emerald Ash Borer:
International Society of Arboriculture:
Plant a Billion Trees:
Society of Municipal Arborists: 
University of Georgia Center for Invasive Species & Ecosystem Health:
USFS Urban and Community Forestry:
Utility Arborist Association: