The British Isles gave birth to porters, stouts, pale ales, bitters, and scotch ales (as well as milds, browns, and others). To a typical American beer drinker who is used to American light lagers, these beers will taste bigger and less "clean," with a variety of hoppy, malty, and fruity undertones. Generally darker, almost always hoppier, fermented with top-fermenting ale yeast, and (often) served at cellar temperatures, British-style ales may seem a little foreign at first - apparently some people don't like the sound of warm, murky beer (PHILISTINES!). If you give them a chance, however, I guarantee these styles will grow on you.
British beers are fermented with ale yeast that, unlike Belgian examples, doesn't produce a huge number of esters or phenols, so (generally speaking) you won't get the wild fruity, spicy complexity of beer from the low-countries. Even so, the different yeasts used do have different characters, English hop varieties are some of my favorites, and when I want a beer, the first things that come into my head are often pale ales and ESBs.
The Beer of an Empire
This phrase is often used in describing British styles of ale, and, while trite and grandiose, there is some truth behind it. India Pale Ale, for example, is so known because standard pale ale had trouble surviving the trip to India and they had to boost the alcohol level and hops (the oils of which have antibacterial properties), which is why we have the strong, hoppy IPAs that we all know and love today. Dark porters and stouts had their genesis during the industrial revolution as the first engineered beers, designed specifically to meet consumer needs, and their success led to the first mega-breweries ever, servicing the thirsty denizens of the British Empire.
The British have exported their beer styles all over the world, and some of the best come right out of America, so don't worry about a beer's pedigree; drink what's good. This article will focus on Bitters and English Pales, which are some of the most widly known and admired styles of beer from the British Isles.
Bitters: Bitters come in three flavors (all of them are beer flavored): "Ordinary," "Special," and "Extra Special (or ESB)." They are made out of essentially the same ingredients and fermented with essentially the same yeast, but they increase in both hoppiness and alcohol content. Ordinary bitters are designed to be thirst quenching and light, and the body and hop flavor increases as the beer gets more "special." If you've never tried an example of this style, try a Redhook ESB - it's certainly decent and widely available. Also, look for Young's Bitter (out of London), and, if you are in the mood for strong flavors that push the boundaries of traditional bitters, Rogue's Brutal Bitter.
Pale Ales and IPAs: Pales can really be classified as another tier of bitters, with more hop flavor and higher alcohol than ESBs. The differentiation between "English Pale Ale," and "American Pale Ale" is an important one. Both Bass (English) and Sierra Nevada (American) are fine beers, but they are wildly different. English Varieties are more subdued: subtler hop aromas and flavors combine with maltier taste to produce a more even flavored beer. India Pale Ales ramp up both the Alcohol and the hop flavor to the point that maltiness is overwhelmed. IPAs will be both bitter and aromatic, and depending on the hops used, will have fruity, floral, grassy, or spicy aromas and flavors (though the bitterness will be what you first taste). Bass Ale is one of my favorite English Pales, and for IPA, check out Samuel Smith's India Ale or Maritime Pacific IPA.
This should get you started in English Beers; next time, we'll talk about Stouts and Porters, as well as that red-headed stepchild of the beer world, Scotch Ale. Happy drinking!