Fungi?

Basics
What are fungi?

King Oyster (Pleurotus eryngii)
mushrooms grow on an artificial log
heavily colonized by white mycelium

Fungi are organisms that belong to Kingdom Fungi. They are not plants or animals, though they are more closely related to animals than plants. They are heterotrophs, so they have to absorb all their nutrients and energy from the surrounding soil, plants, and animals. Fungi can be single-celled (yeast), filamentous (think molds, underground mycelium), and sometimes they can be both depending on their environment and life cycle.

What are mushrooms?
Mushrooms are the reproductive structures (sometimes called fruiting bodies) that some filamentous fungi produce to spread spores. They can be your typical "mushroom-shaped" cap-and-stem with gills or pores, or they can be shelf-shaped, or a gelatinous blob, or an underground lump, or any number of other forms.

What is mycelium?
Mycelium is the very thin thready "root" system of fungi. When you see a mushroom, it is just the reproductive part--the vast majority of fungal cells are in the form of underground mycelium.

Button mushroom (Agaricus bisporus) mycelium grows
onto a tiny particle of compost

Why should I care about fungi?
Many reasons! Not only do they deserve to be conserved, protected, and studied as much as any other kingdom, they have critical roles in ecology and global cycles and have a huge number of current and potential applications. Because many fungi are decomposers, they are critical to the carbon and nutrient cycles. Many other fungi have symbiotic relationships with plants (mycorrhizae, endophytic fungi), and many trees simply cannot thrive, and in some cases, survive, without their fungal partners. Many of our antibiotics are derived from fungi. Mushrooms are delicious nutritional powerhouses, and we depend on yeast for bread, beer, wine, and other fermented foods. The reasons are endless.

Can I eat this mushroom I found in my yard though I don't know what it is?
No. Never eat a mushroom you can't confidently identify.

Your project is about psychedelic mushrooms, right?
No, though I have nothing against them. They are just an incredibly small part of why mushrooms, fungi, and mycology is interesting and important.

A mushroom growing in grass 

Resources - very incomplete
Some of the organizations have Facebook presences as well
Online:
general:
http://www.mykoweb.com/links.html - a pretty comprehensive and slightly overwhelming list of online mycology/mushrooming/cultivation/pathology/you-name-it resources, ranging from intro to advanced

mycology.cornell.edu/fmush.html - a list of mushroom ID resources, ranging from very broad to very specific

reddit.com/r/mycology - small community that posts pictures and articles, and can sometimes give an ID for a posted picture

macrofungal identification:
mushroomexpert.com - an excellent resource for identifying and learning about mushrooms

mushroomobserver.org - upload pictures and information about a mushroom collection, and see info about other collections

namyco.org/clubs - a list of North American mycological societies. Email your nearest one for info about collecting forays and events. The North American Mycological Association hosts annual forays as well

professional societies: 
msafungi.org - website of the Mycological Society of America, which publishes Mycologia (some articles are available open access online) and hosts the Annual Meeting of the Mycological Society of America

ima-mycology.org - website of the International Mycological Association, which publishes IMA Fungus (all open access!) and hosts the International Mycological Congress every four years

taxonomic resources:
cybertruffle.org.uk/cyberliber/ - great online resource hosting/linking out to journals where fungal taxonomic descriptions and revisions are published. Search by author, species, journal, etc.

indexfungorum.org/Names/Names.asp - search for name synonymy, revision history, authors, etc. by taxonomic rank. Main page also links out to other associated resources

mycoportal.org/portal/index.php - search many, many herbaria at once for collection location and metadata of fungal collections


Identification guidebooks: In no way comprehensive, and stilted towards the Southeastern US
Mushrooms Demystified by David Arora - held by many to be the bible of mushroom identification, this book is the most comprehensive general guide currently available but contains complex dichotomous keys that may intimidate some. David Arora has also published some other smaller/less intimidating but still quality ID guides

National Audubon Society Field Guide to North American Mushrooms by Gary A. Lincoff - nice pictures, and is a decent guide for those who don't want to use keys

Mushrooms of West Virginia and the Central Appalachians by William C. Roody - no dichotomous key, but breaks up groups by general macromorphology and has a photo associated with virtually every entry. Includes comments about edibility and easily confused species

Mushrooms of the Southeastern United States by Alan E. Bessette, William C. Roody, Arleen R. Bessette and Dail L. Dunaway - no dichotomous key, and has a section of color plates followed by detailed species descriptions that include microscopic features and chemical color reaction test info


Other books:
Chanterelle Dreams, Amanita Nightmares by Greg A. Marley - at the moment of writing, I haven't finished reading this, but it seems to be a pretty good overview of human-fungal relationships in different cultures

Mycophilia by Eugenia Bone - the author has a pleasant and entertaining writing style, and presents her experiences entering the world of mycology and her interactions with various mycophiles

Pore surface of a bolete