Cask Ale in the Bottle

They may not have the romance of ale served from a beer engine, but bottle-conditioned beers are also real ale. Since they need to keep, bottle-conditioned beers tend to be stronger than the cask-conditioned versions. As the beer should be brilliantly clear, you should decant them off the yeast. It's okay to drink the yeast separately; it's good for you.

English bottle-conditioned ales available in the US

When you can find them, they tend to be expensive, but more often than not, it's worth the hunt. If it has an end date printed on the bottle, take it seriously. Don't save it for a special occasion. Drink up!

Bath Gem
Bluebird Bitter
Entire Butt English Porter
Fuller's 1845
Gale's Festival Mild
Hopback Summer Lightning
Morland Hen's Tooth
Royal Oak
Vintage Henley
Young's Special London Ale
In a special case, Harvestioun Bitter and Twisted doesn't appear to be bottle-conditioned, but it has a third less carbonation than usual.

American craft beers

Bottle-conditioned American beers tend to be stronger--in flavor, alcohol, and conditioning--than the English real ales.

Alesmith beers
Arcadia London Porter, Lake Superior ESB
Bell's Two-Hearted
Sierra Nevada Pale Ale
Stoudt's IPA, Fat Dog Stout, Abbey Triple
Yards Love Stout, IPA

Other bottle-conditioned beers

Most Belgians and Belgian-style beers are bottle-conditioned. Examples include: Ommegang, Unibroue, Chimay, Hitachino Nest, Dupont, Fantome,Westmalle, and Corsendonk.
 
Hefe-weizens and Dunkel-hefe-weizens are wheat beers brewed with a yeast that remains in suspension, clouding the beer. Dunkels are dark versions. Most American wheat beers use a neutral yeast, which is a pity. The German yeast engenders wonderful fruity flavors, starting with banana, pineapple, clove, and bubblegum. For these it's vital to mix in the yeast. You can roll the bottle (gently!) before pouring, or stir up the last inch and pour it in. So far I haven't met a German hefe that I didn't like. These include: Paulaner, Weihenstephaner, Julius Echter, Hacker-Pshorr, Franciskaner, Pinkus, Schneider, Erdinger.
 
Wits are belgian variants of wheat beer, often subtly flavored with spices like coriander or curacao. Examples include: Unibroue Blanche de Chambley, Allagash White.
 
Kellerbiers are the German equivalent to real ale. So far the only example I've found is Mahr's Ungespundet-hefetrub.

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