What Tree is it?
- Tree identification. Especially useful way to work from the shapes of leaves.
- http://www.oplin.org/tree/index.html

About.com - A Tree Leaf Key
- A quick leaf guide for identification of over 50 common North American trees.
- http://forestry.about.com/library/treekey/bltree_key_id_start.htm

Fact Sheets for 680 Trees
- Descriptions, illustrations, US range maps, and cultivation of cultivated species from around the world.
- http://hort.ifas.ufl.edu/trees/

Dendrology at Virginia Tech
- Includes ID keys and fact sheets on over 450 species of wild and cultivated trees in the eastern USA.
- http://www.cnr.vt.edu/dendro/dendrology/main.htm

Plant Kaleidoscope
- Large image gallery of cultivated woody plants in Europe.
- http://www.biologie.uni-ulm.de/systax/dendrologie/

Palm Tree Photo Gallery
- Over a thousand photographs of palms from around the world.
- http://www.junglemusic.net/palmgallery.htm

SelecTree for California
- A tree database for California. Includes non native trees.
- http://selectree.calpoly.edu/

Basics of Tree ID
- A basic guide to identifying trees. Describes leaves, fruits, barks, with many images.
- http://www.fw.vt.edu/dendro/forsite/Idtree.htm

Twig Identification Test
- Interactive identification of leafless twigs and axillary buds. For the trees and shrubs of Ontario.
- http://gaia.flemingc.on.ca/~dhendry/nrtwitst.htm

Foliage Identification Test
- An interactive guide to identifying trees and shrubs of Ontario. Image intensive.
- http://gaia.flemingc.on.ca/~dhendry/nrlfid.htm

Introduction to Tree Identification
- A resource for beginners and others. Includes a collection of descriptive graphics showing leaves, and buds, with notes.
- http://gaia.flemingc.on.ca/~dhendry/trelec.htm