There aren't too many cocktails calling for vermouth as a primary ingredient, but they include some of my favorites like the Bamboo and Chrystanthemum. At home sometimes I make a Reverse Martini (more vermouth than gin), which is said to have been a favorite of Julia Child. As long as you store your vermouth in the refrigerator between uses and throw it out when it spoils (remember, it's a wine), vermouth makes a great cocktail ingredient.
I recently visited the maison of Noilly Prat vermouth, where I sampled some other vermouth-forward drinks, including one that's just equal parts sweet and dry vermouth over ice. Another of their suggested cocktails is supposedly a vermouth spin on the Caipirinha made with dry vermouth, grapes, and sugar, which I tried when I got back home. The drink is nice, but I thought it would work better with some fizz and without the grape chunks.
The drink is very low in alcohol, and refreshing from both the grape juice and the soda water. I was tempted to put it over ice, but I think it will end up too watery. Chill all your ingredients in advance instead.
Vermouth Grape Spritzer
2 fl. oz. Noilly Prat Dry Vermouth, Chilled
6 Seedless Grapes
.5 fl. oz. Simple Syrup
3 fl. oz. Sparkling Water, Chilled
Cut grapes in half and muddle them in bottom of a cocktail mixing glass. Add vermouth and simple syrup. Shake in a cocktail shaker with ice (big chunks of ice are best as we don't want to add much dilution, just extract lots of grape juice) and strain into an old-fashioned or cocktail glass. Add the sparkling water.