I'll be including anything that is too small to see without a microscope in this group.
(With the exception of the slime molds, which I'm including here.)
Phylum Chlorophyta (Green Algae)
Class Chlorophyceae > Order Volvocales > Haematococcaceae
Haematococcus sp.
From the water from the birdbath in the backyard.
Microscosmos: These Algae Curl Up Into a Ball When They Get Stressed Out
Phylum Ciliophora (Ciliates)
Class Colpodea > Order Colpodida > Colpodidae
Colpodidae
Class Oligohymenophorea > Order Sessilida > Voricellidae
Voricellidae
Found in water bowl in yard.
Class Spirotrichea
Subclass Hypotrychia (Hypotrych)
Found in water bowl in yard.
Phylum Mycetozoa (Slime Molds)
Class Myxomycetes > Order Liceales > Family Tubiferaceae
Lycogala epidendrum (Wolf's Milk)
On the spruce stump after a rainy few days.
Phylum Nematoda (Nematodes)
Nematoda (Nematode)
Birdbath/hay infusion
Phylum Ochraphyta
Class Bacillariophyceae (Diatoms) > Order Rhopalodiales > Family Rhopalodiaceae
Epithemia sp.
From iron birdbath
Phylyum Rotifera (Rotifers)
Class Eurotatoria > Subclass Bdelloidea > Order Philodinida
Philodinidae
In a backyard puddle.
Phyllum Tardigrada (Tardigrades)
Class Eutardigrada > Order Parachela > Ramazzottiidae
Ramazzottius sp.
From moss on a log.