Image Uploading to Web Service from iOS

You could check out CloudApp. It started out on desktop but there are a couple good mobile clients as well, namely Stratus and Cloud2go.

These apps don't do any sort of editing. But CloudApp's backend automatically scales images when viewing on a screen that's too small to display them at their native size. Additionally, they provide a 'direct link' option for embedding images directly.

Have you looked into skitch for iOS? I use it extensively for screen shots and it has a sketch.com hosting option and also works well with Evernote and other hosting services. The latter has acquired the former, so you might not be able to make a new account, but you can try skitch out for free on Mac OS as well as iOS.

I could also see using posterous spaces for this sort of thing - they do have an app, but you can just email photos to the web site and it handles thumbnails and processing on the server end of things. Using the service is dead simple and quite pretty layouts are included for free.

You sound like you're looking for a native app, but the web app you access at http://imgur.com/ sounds like the feature set you want. Upload from your camera roll, not linked to you, and you get a url you can paste wherever you want.