Sheep breeds (over) simplified

Sheep were bred over thousands of years to display different wool characteristics. Many breeds mentioned here were already established by the middle ages, and endure also in part because of their excellent adaptation to various climatic extremes. The double-coated primitive breeds first derived from the unique mouflon ancestor have given way in modern times to more specialized ones, so we now don't have to separate the different kinds of coats from a single sheep for different uses but instead use whole fleeces from different breeds. It's helpful for spinners to have an idea of what general characteristics are expected for a breed, so they can make the best use of a fleece, without having to fight what it wants to do all the way, or conversely so they know where to start looking to find the best materials for a specific project.

MOUFLON - the ancestor, long ago eaten to extinction
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PRIMITIVE BREEDS - dual-coated, both coats useful separately or together Navajo-Churro: great tapestry yarns, from a tough little Spanish sheep Shetland and Spelsau: friendly but weather-tough little sheep, fuzzy undercoat; mutually stolen over centuries between Norway and Scotish islands.
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GUARD HAIR SHEEP Indispensable for rugs and upholstery. Long staple, low crimp, lustrous, strong.	UNDERCOAT SHEEP For close-to-the-skin wear. Shorter, high crimp, finer, softer.

Here is a short list of modern breeds, roughly ordered from guard hair to undercoat:
Karakul: indestructible Persian rugs, often coarse and very long
Wensleydale (and many --dales): lustrous rug pile (and stupendous cheese..)
Lincoln: the Rasta sheep, for upholstery, also for strong sweaters and socks
English and Border Leicester: long wool, classic tweedy clothes, English mainstay
Icelandic: long too, low crimp, but softer than most
Romney: good compromise of strength and softness, great in wet climates like US Northwest
Down breeds - Suffolk, Dorset: bad rep as meat sheep, but excellent bounce for blankets etc
Other downs: -- Downs, Cheviot, Welsh mountain: tougher than Downs, but same uses
Corriedale: from New Zealand, the beginner's best friend: lively, soft and easy to spin.
Targhee: Merino with a great bounce, good in dry US Western places
Rambouillet: Merino offshoot from the French, same properties but often cheaper
Merino: the pride of Spanish industry, suitable for non-itchy drawers. No luster at all.

There are also lots of attempts to get the best of both worlds, many of them developed in the 20th century. Columbia, Cormo, Polwarth are examples of well-established crosses of long-hair sheep, usually with Merino to introduce softness. Your mileage may vary in terms of useability.

Remember - individual characteristics can often override breed traits. Racism is just as inaccurate in sheep as in humans, and just as unlikely to predict actual characteristics in practice. We are currently seeing an unfortunate tendency for all breeds to be softened, as farmers try to cash in on the popularity of merino and very soft fleeces. This is a very bad thing for rug weavers, sock knitters etc. Hopefully as spinners get more generally educated we'll see a better balance in the future.