Bartender entrepreneurs are getting really creative with bitters these days. Over the past five or so years they've been making homemade bitters to use in cocktails at their bars, and now they're making some of those bitters available for sale.
Probably the largest variety of bitters can be found online at CocktailKingdom (most liquor stores only carry one or two brands of bitters at most), where they come in abstract flavors including Jamaican Jerk, Elemakule Tiki, and Tobacco.
Many of the ingredients in bitters, which are used just in dashes in cocktails to tie a drink together, are naturally bitter herbs, bark, and citrus peel, like quinine, wormwood, and grapefruit. At some point someone realized that celery, too, is naturally bitter, and now several brands of this flavor have hit the market.
Celery bitters work really well in a Bloody Mary, in a vodka or gin Martini, and in a Gin & Tonic. A recipe for a minty, herbaceous version of the latter cocktail made with celery bitters is below.
Garden & Tonic
Created by Wayne Collins and Naren Young
1.5 fl.oz. Gin
2-3 dashes The Bitter Truth Celery Bitters
2-3 dashes Elderflower Liqueur or Maraschino Liqueur
4-5 Mint Leaves
1 Slice of Cucumber
1 Lime Wedge
Put all ingredients in a highball glass on ice and fill up with tonic water.