This is a work-in-progress D3 slopegraph "editor" in response to a "challenge" by @edwardtufte : http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0003nk
It runs locally in the browser (no uploading to a server required), but that means using a modern browser. I've tested it in the latest Chrome, Safari & Firefox on OS X Mavericks. YMMV
It needs work but is a decent framework.
You can drag individual labels around on the axes, but I need to get "collision handling" working.
Live preview at: http://rud.is/workbench