Flickr.com is free and can be used with credit/link if the photog says “Public” and “Some rights reserved.”
MorgueFile is free and they only ask us to credit the photographer “if possible”. So we don’t expect the quality to be super-high, though you never know.
U.S. Fish and Wildlife Service images are free.
NOAA photo library is free.
Missouri Botanic Garden site indicates that small size images are free with credit and link given (“Photo courtesy Missouri Botanic Garden”, with link to the page the photo came from).
BY PAID SUBSCRIPTION
All these work on a credit system, and I’ve paid for the minimum amounts of credits in advance. All are $1 per credit except iStock, with is $13 for 10 credits. Blog-size photos usually cost 1 credit. If credits have run out, feel free to order another bunch, but let me know.
Fotolia ID: susanharris Password: ranters4 (minimum credit buy is $20)
123rf.com User name: gardenrant Password: ranters4 (minimum credit buy is $15)
Stock expert Sign in: susanharri (Note there’s no S at the end of my name) PW: ranters4
email address: firstname.lastname@example.org (Minimum credit buy is $5)
iStock Login as: SustainableSusan PW:oberlin71
Email given is email@example.com Minimum credit buy is $13
NOT USABLE FOR US
PicApp.com is free, seems too good to be true, and the catch is that you embed code, and with the code comes ads.
Photo shelter photos cost $75 and up.