Photobucket, been using it for years. Only once did it falter but I didnt loose any pic at all, its what I use also to host the pic in my signature

Its easy to use, easy to register - free. There's also a food user friendly editing system to it so you can easily resize and touch up your pics before posting here. I usually re size my pics or crop them coz my camera always shoots em in biiiig photo size.