Layered beer drinks might not be fitting to speak of on a cocktail blog, since however you want to define “cocktail”, they won’t fit the bill. We only have two ingredients, neither of which are liquor, and we’re not doing any work to mix the drink. They can’t really be called highballs, either. But they’re drinks, they’re asked for regularly, and if you can pull them off, your guests will be very impressed. All of these drinks involve layering stout (usually Guinness, though there are other good options) over a half-glass of something else.
First, the Black and Tan, made with stout and ale. This drink is usually associated with the Irish, though it shouldn’t be, for two very important reasons: first, the “Tan” is usually Bass, an English ale, which no proper Irishman would mix with the black stuff; second, the Irish don’t have the best association with the phrase Black and Tan. Wikipedia tells me that in Ireland, your barkeep would probably use Smithwicks (also made by the Guinness people), and would call it a Light and Bitter. (Or anything other than “Black and Tan.” It’s probably the most offensive thing you could say to an Irish bartender this side of an Irish Car Bomb.)
The Half and Half is a bit more Irish, as it’s usually made with Guinness and Harp Lager (again, made by the Guinness parent company.) Harp is actually a Vienna-style lager, but they call it Irish, so we might as well do the same.
Then you’ve got a Black Velvet, which was originally devised as a stout-and-champagne combination, but is now usually made with stout and cider. (You can use any cider you’d like, but if you want to stay with the Irish theme, I’d go with Magners.) And we haven’t mentioned any of the lesser layered drinks. Magic Hat #9 and Guinness can be called a Black Magic; Blue Moon and Guinness makes a Dark Side of the Moon; pumpkin beer and Guinness will occasionally be called a Black-o-Lantern.
Whatever mixture you’re using, here’s a pretty good video showing just how to layer your beer. Though again, if you’re going for the Irish style, many bartenders there don’t bother to layer the beer at all.