-- field key --

7 Collybioid / Marasmioid:

Cap fleshy, typically small;

stem thin and either cartilaginous, wiry or bendable. 

Gills attached to nearly free. 

Veils absent.

Tuberous Collybia
Collybia tuberosa
Collybia (Gymnopus) dryophila, attacked by the jelly
fungus Syzygospora mycetophila

Collybia semihirtipes
Spotted Collybia
Collybia (Rhodocollybia) maculata

Platterful mushroom
Tricholomopsis (Collybia) platyphylla
Cyptotrama (Collybia) asprata

Rooted Oudemansiella
Xerula (Oudemansiella) radicata
another, with Don Shernoff

Velvet foot
Flammulina (Collybia) velutipes

Fairy ring mushroom
Marasmius oreades
Pinwheel Marasmius
Marasmius rotula

Look-alikes include Leptonia (Entoloma), Agrocybe pediades, etc.
Hemispheric Agrocybe -- brown spored
Agrocybe pediades
brown spored
Tubaria sp.

Bluing Psilocybe -- purple-brown spored
Psilocybe cyanescens
pink spored
Leptonia (Entoloma) sp.

Bricktop -- purple-brown spores
Hypholoma (Naematoloma) sublateritium
Sulfur tuft
Hypholoma (Naematoloma) fasciculare