This site is the best in my opinion.
Although it is in another language, it never resizes your image, very quick to upload usually and you do not need an account. It does not give you the image codes, but you can put them in by clicking the "insert image" button when posting.
SIMPLE INSTRUCTIONS ON HOW TO USE ABLOAD: Bilder von der festplatte hinzufugen basically means "browse", or find the image I want to upload.
Then press the big button that says "Abload!" which pretty much means upload.
Dont bother fiddling with the other settings.
The next best option, if you are uncomfortable using the site above. It IS in english, no need to join and doesnt resize, however I find that it is the slowest to upload an image. To be honest, I am unsure if this gives you the image codes or not.
This one you need an account for, but it is the most user-friendly. It is easy to use and even gives you the image codes. It is quite slow to upload though, and it resizes your images with common png compression.
This one you don't need an account for and is sorta average to upload. However it resizes your images. It also gives you the image codes.