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/

American Penstemon Society
- Offers information about membership, library, publications, and events, along with a photo gallery.
- http://www.penstemon.org/

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

The Penstemons: Seed Germination Methodology
- Two pages in Tom Clothier's extensive 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

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

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

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/