If its about photo sharing ,there some factors come within ,such as uploading an image,storing it,ease of sharing,enough allocated space plus social feature friendly which is a common trend now.
Best websites to store,share photo images
Google+/former Picasa web
Former Google Picasa is merged with Google+.Picasaweb/Google+ is the best for free photo storage and sharing.Google+ offers free 1 GB storage,but image below 2048by 2048 px will not count to space.
That is if all your image is below that limit,you have unlimited storage in Google+,but for this you need to have a Google+ account.
The upload interface is good enough and it has become social friendly,now people can share,tag,make comment on image but need a Google+ account to get all this.
There is a desktop application of PicasaWeb called Picasa,which is amazingly fast for simple photo editing and sync to Google+ web album to upload images to web from desktop directly.
Links related to Google+ image upload/share
Flickr
Flickr is one of the best photo sharing website from Yahoo.com.Professional photographer around the world prefers flickr to share ,sell & show off great photos.