I guess it depends what you like......here are a few suggestions.
~ Pick a favorite movie and base everything off of it.For example The Sisterhood of the traveling pants. You could have a slumber party and watch the movie. Then have your best friends decorate jeans.
~ You could take your friends shopping at the mall.Have them each bring x amount of money and have a shopping spree. Celebrate with pretzels or ice cream from the food court.
~ Have a classic slumber party. Have pizza,watch hours of movies, and sleep in as late as you want.
~Go out to eat at a favorite restaurant.
~Have a boy-girl party.Have dancing and great music and food.
Well that's all i can think of. Hope I helped!!!!!