Neurospora is a genus of filamentous fungi or mold which grows on burnt or decaying plant matter. It is used as a model organism for studying biochemistry, genetics and molecular biology.
The species in this genus are numerous and cosmopolitan; hundreds of different strains are also available for research from collection efforts worldwide. Neurospora is easy to grow and maintain in culture in the laboratory. The most commonly-used species is Neurospora crassa (it's the cause of pink bread mold) but other species within Neurospora are also used.
The full taxonomic classification of Neurospora is:
Kingdom Fungi (or Myceteae in some literature)
Division Amastigomycota
Subdivision Ascomycotina
Class Ascomycetes
Subclass Hymenoascomycetidae
Order Xylariales
Family Sordariaceae
Some or all of the information in this writeup was taken from the science dictionary at http://biotech.icmb.utexas.edu/; I oversaw the development of the dictionary (the website was mothballed in 1998) and I believe I wrote the entry this is based on.