Trees of Antiquity
Heirloom apples, also stone fruit, pawpaw, pecans, grapes, kiwi. USA zone adaptations given for each fruit variety.

TreeWeb: The Natural History of Trees
Includes information about almost all North American trees, with brief descriptions, range maps, and a few images.

Trees for the Future
Trees for the Future is a non-profit organization initiating and supporting agroforestry self-help projects in cooperation with groups and individuals.

The National Arbor Day Foundation
A well-known organization with a mission to inspire people to plant, nurture, and celebrate trees.

PLANTS National Database
Check out the USDA's extensive online database for all kinds of plants.

Treelink: The Urban Forestry Portal
A non-profit group working to improve urban and community forests by providing Internet-based information, tools, and inspiration.