I would recommend the British lichen flora for a key that includes our common species.
Actually, I would recommend this as an indispensable book for anyone trying to identify crusts in the northern Hemisphere.
Plus see information and photos on a couple of additional but rarer species in:
Spribille, T., B. Klug & H. Mayrhofer. 2011. A phylogenetic analysis of the boreal lichen Mycoblastus sanguinarius (Mycoblastaceae, lichenized Ascomycota) reveals cryptic clades correlated with fatty acid profiles. Molecular Phylogenetics and Evolution 59:603-614.