Image hosting is main focus for web developer and general internet user also, Web Developer using image hosting for reduce server load of website and speedup their site.
General internet user used image hosting site for share image to friends and family but for hosting image you must have to pay for server (hosting) but many of popular image hosting service is available for free. you don’t need to pay money for file hosting specially for image.
Picasa is one of the popular image hosting site , it provide free image hosting.Picasa provide free image hosting for everyone.it also allow you to edit image and apply different types of effects. you can also download Picasa Desktop application for picture preview and editing.
Photobucket is free image and photo hosting site . along with free hosting it is also marketplace for photographer. if you are photographer then you can sell your picture for commercial use.you can use free high resolution image for any user (public Licence)
Flicker is my favorite site for image hosting and image searching site. Photobucket is also pretty and best but i am using flicker more than Photobucket.you can create album and share to friends, even you can make group of images (gif image hosting is allowed)