It's colorful (deep red in color actually) history of its discovery and acceptance is detailed in that blog: from the Campari bar in Florence in the 1860's through Count Negroni in the early 1900's.
The drink, pictured above, consists of equal parts of Campari, sweet vermouth, and gin, plus a slice of orange, generally.
Now, thanks to an article in the recent La Cucina Italiana, we have another variation, the Sbagliato, which translates into the 'mistaken' Negroni. According to the magazine, in a bar in Milan, the proprietor reached for a bottle of spumante rather than gin. The bubbly was tried, and received wholehearted approval.
Here is the official Sbagliato formula, courtesy of La Cucina Italiana:
one ounce campari
one ounce sweet vermouth
one ounce dry spumante (prosecco)
Fill a rocks glass with ice, add the Campari, vermouth and spumante in that order. Stir and add an orange slice.
Eccola! . . . perfect for summer.