Below are names of professional mycologists that can be approached to possibly identify mushrooms that you could not identify any other way and you suspect that it might be a new specie.  You should first try to identify the mushroom yourself.  If that does not work, try posting to a discussion group where there are some experts.
I recommend that you post pictures of your mushroom to the internet.  Make sure to get a spore print.  Then write the mycologists and ask him or her to look at your pictures to see if he/she can recognize your mushroom.  Also include the spore print color and things like the size of the cap, where the mushroom was found etc.  The more information you can give about the mushroom the better.  If it looks like it might be something unusual or new to science he/she will ask you to ship a dried specimen.  Ask him/her for instructions on drying and shipping.
1 - able to help with identification only
2 - able to help identify and write up new species
3 - instructions from mycologist
4 - did not reply to e-mail

William G. Allan   McGill Univ., 21, 111 Lakeshore Rd., Ste-Annede-Bellevue, QC. H9X 3V9, Canada.
Brian P. Akers   4   Dept. of Biology, St. Andrews Presbyterian College, 1700 Dogwood Mile, Lauringburg, NC 28352
Daniel L. Lindner   2 wood-inhabiting fungi
Timothy J. Baroni  4 Entolomataceae, and boletes
Rodham E. Tulloss  2   3 Amanitaceae
Roy E. Halling   4 Agaricales and Boletales  
Gregory M. Mueller Laccaria
Amy Rossman Ascomycetes Curator USDA Syst Bot
Bill Roody  4 macrofungi
Ernst E. Both  4 Boletes  
Richard Harris Lichens NYBG
Stephen Bentivenga Zygomycetes University of Wisconsin @ Oshkosh
Rick Bortnick Water moulds Delaware Valley College
George Carroll Endophytic ascomycetes University of Oregon
Dennis Desjardin   4 macrofungi San Francisco SU
Jonathan Dey Lichens Illinois Wesleyan University
Robert Fogel Basidiomycetes University of Michigan, Ann Arbor
Glen J. Freeman macrofungi  
Larry Grand polypores and resupinates North Carolina State U
James E. Johnson Basidiomycetes Duke University
Dave Largent macrofungi Humboldt SU
Rosalind Lowen Pyrenomycetes NYBG
Coleman McCleneghan macrofungi Appalachian SU
Andy Methven macrofungi Eastern Illinois University
Steve Miller macrofungi University of Wyoming, Laramie
Jack Murphey macrofungi Deep Springs College
Karen Nakasone Wood-decay fungi USDA-FS Forest Pathology Lab Madison, WI
Ronald H. Petersen macrofungi University of Tennessee
Scott Redhead macrofungi Curator,Canadian National Mycological Herbarium
Gary Samuels Ascomycetes Research Scientist Syst USDA Syst Bot/Myc Lab Beltsville, MD
Carol Shearer Ascomycetes University of Illinois Urbana, IL
Walt Sundberg Lepiotaceae Southern Illinois U
Greg Thorn macrofungi University of Wyoming Laramine, WY
Rytas Vilgalys macrofungi Duke University
Thomas Volk  4 Wood decay fungi  University of Wisconsin, Dept. Biology La Crosse