- Field guides - they all claim to be complete or comprehensive and none of them are as they only contain a tiny fraction of fungi species
- Collins Complete Guide to British Mushrooms and Toadstools - not at all complete, but compact and good for its size
- Encyclopedia of Fungi of Britain and Europe - Michael Jordan - a bit big for the field, but has some useful features such as a key to species, a colour chart, some fungal anatomy as well as more species than the Collins "complete" guide
- "Mushrooms: A Comprehensive Guide" (Roger Phillips)
- Collins Fungi Guide - this is the most comprehensive of the field guides, covering 2,400 species. It has colour illustrations, rather than photos.
- Technical literature
There are too many more to be listed here, but here are some of the best known ones. Most available from Summerfield Books or the NHBS.
- Funga Nordica - out of print. This is "the bible" of identification for cap and stem fungi (Basidiomycetes only) - it has no photos, only drawings of microscopic details, but it has excellent keys to 3,500 species. (UPDATE: This is due in 2017 according to the publishers...not so soon, as of writing http://nordsvamp.org/ )
- Fungi of Switzerland - a beautiful set of (very expensive) books, and the most comprehensive illustrated set of books on fungi
- Kibby guides - a useful set of small books on particular genera. Currently guides on these genera: Russula, Amanita, Agaricus, Tricholoma, "Boletes" and "British Milkcaps."
- Online resources
- Mycokey - a free online key to help get to genus
- BMS keys to macro fungi
- Outer Hebrides Fungi
- The fungi of southern England - Leif Goodwin
- Fungi of the New Forest
Sites devoted to particular groups of fungi
- Pyrenomycetes of southwest France
- Boletes -The Boletales
- Inocybe - http://www.inocybe.org/
- Leccinum - http://www.entoloma.nl/html/leccinum_eng.html
- Psathyrella - http://www.vielepilze.de/
- Coprinus s.l. - http://www.grzyby.pl/coprinus-site-Kees ... prinus.htm
EDIT : added some suggestions for sites on fungal groups