digiKam - Professional Photo Management with the Power of Open Source
Flickr - image and video hosting website
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Imgur - Imgur is a free and simple image hosting service with image editing feature. Signup is optional.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Google Photos - All your photos are backed up safely, organized and labeled automatically, so you can find them fast, and share them how you like.