Permanent Marker Removal for cotton clothing - As soon as possible, spray the mark liberally with hair-spray. Allow to sit for one minute then rinse in clear warm water. If some stain remains, repeat, until all stain is removed and then launder as usual. A friend of mine suggested this to me and it works great!
I've just tried it on my pricey raincoat made of 100% polyamide. It worked pretty good. I can barely see the stain now. Half way through, I started to spray on both sides of the fabric. The only drawback is that it had took me almost an hour to accomplish this.