Yikes, that's a tough one. According to one of my favorite household books, 2,001 Amazing Cleaning Secrets by Jeff Bredenberg for Reader's Digest, you have to do the following multi-step process, for which you will need dishwashing liquid, water, a clean rag, paper towels, something heavy (like a small pile of books), plastic wrap or aluminum foil if your heavy item needs protecting from moisture, and a spray bottle (with plain water inside).
First, mix 1/4 tsp. dishwashing liquid with a quart of water, dip a clean rag into the solution, then use a blotting motion to work the solution into the stain. Blot with a clean, dry paper towel. Spray with the water. Blot again. Continue to spray and blot until the suds are all gone. Finally, spray one more time with water, but don't blot this time. Instead, lay a pad of clean, dry paper towels over the area, top the towels with the wrap or foil (if necessary), then top that with the heavy item. Let it sit like that until it's dry.
Once dry, if the stain is still there, start over again, but this time use 1/2 tsp. dishwashing liquid for the first step.
Once dry, if the stain is still there, try moistening the area with 3 % hydrogen peroxide, let it stand for an hour, then blot and repeat until the stain is gone. You don't have to rinse, but do dry the area by using the paper towel procedure described above.