Line a strainer with 4 layers of cheesecloth; place over a bowl. Add yogurt to strainer; cover yogurt with edges of cheesecloth. Refrigerate for 8 hours or overnight.
In a large saucepan, combine the rhubarb, 1/2 cup sugar, water, vinegar and salt; cook over medium heat for 12-15 minutes or until sugar is dissolved and rhubarb is tender. Transfer to a bowl; cover and refrigerate until chilled.
In a large bowl, beat cream until it begins to thicken. Add vanilla and remaining sugar; beat until stiff peaks form. Transfer yogurt from cheesecloth to a bowl (discard liquid from first bowl). Gradually fold cream mixture into yogurt.
Fold into rhubarb mixture. Spoon into dessert dishes. Cover and refrigerate for at least 1 hour before serving.