The level editor for Super Meat Boy on PC may not be available until sometime in January, but the DevTools ARE there for you to mess around with and some people have been making some very, very incredible levels with it. However the DevTools are not the easiest thing to use, and there isn’t a GUI to help you out. YouTube user GproductionsOh has gone ahead and made a nice two part video guide which I’ve embedded after the break. He even added some nice little animations to the instructions, it feels like an official tutorial!
If you simply can’t wait for the official Level Editor and simply want to start cracking some stuff out now, this should help you out quite a bit!