I went through this exercise a couple of months back, here is the 24hcf thread.
"Which free hosting site" Some good info in the thread info. I ended up using "Flickr" parting because I already have a Yahoo account and it was easy. But also because I'm just starting to use LightRoom5 and it has a built in "hook" to link to and upload to Flickr... I like easy.
Enjoy,