that would probably be better as an app, rather than a hosted service.

I run picsur. It’s not an image resizer like that. It’s like Imgur, but self-hosted and can take size arguments as part of the query. I use it to host images for a markdown based blog and keep the sizes under control.

On a side note, I recently started noticing so many sites that use full sized images regardless of the actual size it shows up on screen.

Can you share some screenshots? It sounds like you’re not even reaching the service.