Other Citrus Fruits from On Food and Cooking by Harold McGee

Lesser-known citrus fruits that are worth knowing about include the following:

C. x aurantium, Bergamot possibly a cross between the sour orange and sweet lime (C. limettoides), is grown mainly in Italy for its floralscented rind oil. It was one of the components of the original eau de cologne developed in 17th-century Germany, and is mainly used in perfumes, tobaccos, and Earl Grey tea.
Kumquats, species of the genus Fortunella, are bite-size fruits that are eaten whole, thin rind and all. They are generally tart but not bitter. The calamondin or calamansi, also a diminutive citrus, is probably derived in part from the kumquat.
The finger lime, Microcitrus australasica, is a small, elongated citrus relative native to Australia. Its fruit has robust, decorative round juice vesicles that can be pale or pink-red, and a distinctive aroma.
The makrut or kaffir lime, Citrus hystrix, is common throughout Southeast Asia. Its rough green peel has a limelike aroma with general citrus and pine notes (from limonene, pinene), and is used to flavor various prepared dishes, as are its intensely lemonscented leaves.
The tangelo and tangor are modern hybrids between the tangerine and grapefruit, and tangerine and orange, with hybrid flavors as well, and mostly eaten as fresh fruit.
The yuzu, citrus x junos possibly a mandarin hybrid, came from China but was developed in Japan beginning around a thousand years ago. The rind of the small yellow-orange fruit is used to flavor various dishes, and to make vinegar, teas, and preserves. It has a complex flavor that includes musky sulfur compounds, and clove and oregano notes (from the phenolics eugenol and carvacrol).