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)
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.