BackyardGardener.com: Garden Guides on Plants  
   Starting point for information on (types of) plants, with summary information for many species and varieties.
   http://www.backyardgardener.com/plants/

WeedAlert.com  
   Offers a weed listing for the United States regions, primarily weeds occurring in lawns.
   http://www.weedalert.com/

Findmeplants.com  
   Garden plant finder. Search by specifiying garden conditions and design requirements such as flower color, size and growth habit. Search results include plant photo and summary information.
   http://www.findmeplants.com/

Cal's Plant of the Week  
   Features a new plant every week, with photo, description, and cultural information. Previously featured plants can be selected by botanical or common name. Focus is on plants for greenhouse culture.
   http://www.plantoftheweek.org/

The Garden of Paghat the Ratgirl  
   Pacific Northwest gardener presents essays for hundreds of species growing in her garden, with personal notes, history, cultural information, and photos for each.
   http://www.paghat.com/

FloraFinder.com  
   Offers links to gardening websites arranged by plant type, with a brief description of each site.
   http://www.florafinder.com/

DenverPlants.com  
   This resource for gardeners in the Denver metro area includes a sizeable database of plants with photos and cultural information.
   http://www.denverplants.com/

Plants Database  
   Online USDA database of botanical information, images, and links on plants in the USA, including crops and invasives. Search by name, geographic distribution, or other characteristics.
   http://plants.usda.gov/

HortiPlex  
   Horticultural database with over 100,000 species and cultivars. Comments, ratings, and photos for many varieties supplied by members of the Gardenweb community.
   http://hortiplex.gardenweb.com/

Plantfacts.com  
   Searchable database of plants with information on flowering, and climate.
   http://www.plantfacts.com/

Gardenline  
   Guide to growing and caring for houseplants, vegetables, trees and shrubs. Also features common pests and a miscellaneous section. From the University of Saskatchewan Extension.
   http://www.gardenline.usask.ca/

Echo: Fruiting Trees, Shrubs, and Herbaceous Plants  
   Features cultural information, uses, handling tips, and links for an extensive list of fruits and vegetables.
   http://www.echonet.org/eln&herbs/eln_catalog/eln_index.htm

Fruits and Vegetables  
   Extensive set of fact sheets and links from the University of Florida.
   http://edis.ifas.ufl.edu/TOPIC_Fruits_and_Vegetables

Horticopia On-line Plant Information  
   Extensive directory of plants, categorized by genus, includes summary cultural information and small photograph for each plant.
   http://www.horticopia.com/hortpix/

Shiraz Gardeners' Guide  
   Gardening resource site with an extensive plant directory featuring photos and cultural information.
   http://shiraz.me.uk/

Floridata  
   Features hundreds of plant portraits, each illustrated with several photos, documenting the garden uses and cultural requirements of each species or cultivar.
   http://www.floridata.com/

PlantZAfrica  
   Extensive information about plants native to southern Africa, including hundreds of alphabetically arranged plant portraits, by the National Botanical Institute of South Africa.
   http://www.plantzafrica.com/

Foliage Plants Database  
   Searchable database with basic information and some photographs of plants grown primarily for their foliage. Japanese and English.
   http://albinopri.cool.ne.jp/leaf/en/

Gardenweb: Name That Plant  
   Forum that allows users to upload images of plants that they are trying to identify.
   http://forums2.gardenweb.com/forums/namegal/

Tiscali Gardening  
   A South African flower, plant and gardening portal with searchable plant database, photographs and information.
   http://www.tiscali.co.za/

Dave's Garden: PlantFiles  
   Database with over 80,000 plants with cultivation information and pictures supplied by member gardeners.
   http://davesgarden.com/pf/

Illinois' Best Plants  
   Chicago Botanic Garden provides a database of recommended plants for Illinois gardens, from perennials to trees, with photos and information on their culture and use.
   http://bestplants.chicago-botanic.org/

All America Selections Winners  
   Showcases new varieties of flowers, vegetables, and plants for garden performance.
   http://www.all-americaselections.org/