I found the attached information on removing Sharpie stains at the company's (Sanford) internet site. I have also had excellent luck remving Sharpie ink off furniture using Carbona #5 (fat, grease & oil) spot remover. Carbona can be found in most grocery stores.
"To remove most stains from most surfaces, Sanford recommends you try Amodex® ink and stain remover.
Your best chance at complete stain removal with all Sanford inks on all surfaces is to use Amodex! It removes virtually any ink or food stain on virtually any fabric or surface. Best of all, it will work as well after two weeks as it will after two hours - so it is probably worth the wait for your favorite or expensive garments. If you plan to use Amodex, do not attempt to treat the stain first - even rinsing in water can reduce the solution's effectiveness."