I think that the only way to e-mail a photo is to start at the photo (in the 'photos' app), and select 'e-mail photo'. I don't think you can start an e-mail and then embed a photo in it. As far as posting to a site like this, I don't think you can do it as an attachment because you'd have to be able to 'browse' your photos from within Safari. You could link to a file (using 'insert image') that's hosted somewhere else, though.