I normally use 'Tinypic' to post images, but it's been playing up, as it does now and then, so after trying a few free sites which were not great, I found 'Postimage.org' that works a treat (so far ).
http://postimages.org/
As I say, it's free and you need no account, nor do you have to give your details. Just remember to choose your image size on the first page before you upload.