I found this on our Heirloom Recipes board. Great for a summer party. Yum!
http://messageboards.ivillage.com/n/mb/message.asp?webtag=iv-fdheirloom&msg=7152.1&ctx=0
3lbs. red potatoes, washed, chopped and cooked until tender
3/4C mayo
1/2C sour cream
2-3TBS. vinegar (I used rice vinegar)
1TBS sugar
1/2teas. salt
1/2 teas. garlic powder
1teas. pepper
1 bundle of green onions, just the tops/greens
Mix all ingredients together then pour over cooled potatoes and mix. Chill at least 4 hours but better if chilled overnight.