I'm a fan of mixing equal parts of jam and vinegar, then bringing 'em to a boil. The kind of jam and vinegar is up to you, however I avoid balsamic because it is too heavy. Balsamic vinegar boiled down by itself into a syrup is good for drizzling over stuff like strawberries. Roland, the gourmet foods company, makes a tasty balsamic syrup that does the work for you. I'm a huge fan of Thai sweet chile sauce. To me it is the perfect balance of sugar, vinegar, heat and garlic. Best of all, it sells for a couple of bucks for a quart at most Asian markets. Can't hate that!