owls:
Hedwig - Harry's snowy owl, amber eyes, unusually intelligent
Erroll - Weasley family's owl, old and decrepit
Hermes - Percy's screech owl
Pigwidgeon - Ron's (Scops?) owl (GF) tiny, over-exuberant
school owls - various owls which can be used by students to send mail
Malfoy's eagle owl
types of owls:
     Eagle, Scops, Tawny, Screech, Barn, Brown, Snowy
stores that sell owls:
Eeylops Owl Emporium (Diagon Alley)
     where Hagrid bought Hedwig for Harry (SS5)
Magical Menagerie (Diagon Alley) 
     Hermione goes here to buy one but ends up with Crookshanks (PA
Owl Post:
hundreds of owls deliver mail every morning during breakfast at Hogwarts
Post Office - Hogsmeade
     rows and rows of owls of all sizes, color coded - you choose how fast 
     you want your message delivered
Post Owl
Owl Order
newspaper delivery
     the owl has a small pouch on its leg for coins (SS5)
     Hermione receives the Daily Prophet this way (GF
other:
Owl Treats - Ron feeds these to Pigwidgeon
Owlery
The Owlery, where the school owls and the owls belonging to students live, is located on the top of West Tower (GF15).

The Owlery was a circular stone room, rather cold and drafty, because none of the windows had glass in them. The floor was entirely covered in straw, owl droppings, and the regurgitated skeletons of mice and voles. Hundreds upon hundreds of owls of every breed imaginable were nestled here on perches that rose right up to the top of the tower, nearly all of them asleep, though here and there a round amber eye glared at Harry. He spotted Hedwig nestled between a barn owl and a tawny, and hurried over to her, sliding a little on the dropping-strewn floor. (GF15)

web link: "The Owls of Harry Potter" from "Arabella Figg's Hogwarts Express" website.