There are some apps that can do it, but the ones I've found are photo editing apps. Photo bucket has an app to post to their site and you could then do the link to that from a post here. The app doesn't have the greatest reviews, though.
I googled 'posting photos to Internet from ipad' to find the apps. I haven't chosen one yet.
I know it is an extra step but I send pictures directly to Facebook and then download them to my computer. Then you can upload them to attach to post. you could email them to yourself too. I know, it's a pain but this way I don't have to pay for extra apps.