Penstemon

American Penstemon Society
Offers information about membership, library, publications, events, taxonomy, and illustrated identification characteristics.
http://www.apsdev.org/

Dave's Garden PlantFiles: Genus Penstemon
Index page with links to all species and varieties of penstemon listed in the PlantFiles database of member-provided plant information and photos.
http://davesgarden.com/guides/pf/b/Scrophulariaceae/Penstemon/none/cultivar/0/

Kemper: Penstemon digitalis
Plant portrait of foxglove beardtongue with cultural information, photos, and noteworthy characteristics.
http://www.mobot.org/gardeninghelp/plantfinder/Plant.asp?code=G590

Las Pilitas: California Penstemons
Two pages with pictures, brief descriptions, and cultural requirements of penstemons native to California, for dry-area and moist-area species.
http://www.laspilitas.com/groups/penstemon/california_penstemon.html

Paghat's Garden: 'Bashful' Beard-tongue
One of a series of plant portrait pages documenting penstemons in this Pacific Northwest garden. Varieties featured are 'Bashful', 'Prairie Dusk', 'Midnight Blue', 'Ruby', 'Apple Blossom', 'Sour Grapes', and 'Garnet'.
http://www.paghat.com/penstemonbashful.html

Penstemania
Based on Penstemon growing and the Western Algarve.
http://www.penstemania.co.uk/

The Penstemon Website
Enthusiast's collection of links, information (both for gardeners and botanists), and photographs of penstemon species and varieties.
http://www.biosci.ohio-state.edu/~awolfe/Penstemon/Penstemon.html

The Penstemons: Seed Germination Methodology
Two pages in Tom Clothier's plant germination database dedicated exclusively to penstemon species, which are often finnicky and require a wide variety of germination conditions.
http://tomclothier.hort.net/page08.html