UK & Ireland
Fungi of Great Britain and Ireland - fungi.myspecies.info
Mike Sutcliffe's Photo Library - www.britishlichens.co.uk
Lichen Ireland - www.habitas.org.uk/lichenireland
Lichens of Ireland - www.lichens.ie
Irish Lichens - www.irishlichens.ie
Lichens of Wales - wales-lichens.org.uk
Scottish grey literature - tinyurl.com/68wdmbl
Cumbria Lichen and Bryophyte Group - cumbrialichensbryophytes.org.uk
Nature in the Yorkshire Dales (including lichens) - www.natureinthedales.org.uk
A key to common lichens on trees in England - PDF
Europe and Scandinavia
Italian lichen keys - dbiodbs.univ.trieste.it
Lichen Herbarium Photolibrary, University of Oslo - www.nhm.uio.no/lav/web/index.html
Lichen Gallery: Leif & Anita Stridvall - www.stridvall.se/lichens/gallery
The Lichens of Greece - www.lichensofgreece.com
North America
Lichens of North America - www.sharnoffphotos.com/lichens/lichens_home_index.html
Farlow Herbarium, Harvard - huh.harvard.edu/pages/farlow-herbarium-fh
Tropical
Tropical lichens - www.tropicallichens.net
Tropical Lichens & other keys worldwide - www.bgbm.org/sipman/keys/default.htm (these keys are free and cover many areas with relevance for BLS based in or traveling to overseas locations)
Worldwide
Checklists of lichens worldwide - www.lichens.uni-hamburg.de/lichens/portalpages/portalpage_checklists_switch.htm (Internet archive)
Checklist of lichenicolous fungi worldwide - www.lichenicolous.net
Lichen Study Courses
(see also the BLS Events calendar for BLS workshops etc.)
Field Studies Council re lichen courses - https://www.field-studies-council.org/biodiversity/lichen-identificatio…
Recording & Mapping
National Biodiversity Network - www.nbn.org.uk
NBN Atlas - https://nbnatlas.org/, and for helpful documentation on using the Atlas https://docs.nbnatlas.org/
iRecord - www.brc.ac.uk/irecord
iSpot, a website aimed at helping anyone identify anything in nature - www.ispot.org.uk
Air Pollution
OPAL, the Open Air Laboratory project - www.opalexplorenature.org/AirSurvey
Encouraging lichens in the garden
A Likin' for Lichens - www.abc.net.au/gardening/stories/s4514895.htm
Journals and Magazines
British Wildlife - www.britishwildlife.com
Related Organisations & Societies
Plantlife - www.plantlife.org uk.
The British Mycological Society - www.britmycolsoc.org.uk
Royal Society of Biology - www.rsb.org.uk
The Linnean Society - www.linnean.org
The British Bryological Society - www.britishbryologicalsociety.org.uk
International Association for Lichenology - www.lichenology.org
Literature
Recent Literature on Lichens - nhm2.uio.no/botanisk/lav/RLL/RLL.HTM