2 lbs of Red Bliss potatos, cut into 1 inch chunks (leave skin on)
2-3 TBS balsamic vinegar
1 TBS dijon mustard (or mustard of choice)
1 tsp olive oil (could be omitted)
fresh ground pepper

Boil potatos until fork tender, but not mushy.  Drain, and add other 
ingredients and mix gently.  You could probably experiment with the spices, 
and add dill, or basil for a change, or garlic.  Serve warm or cold (I 
preferred cold).  My SO, who eats low-fat but is not religious about it, 
thought it was great!