There are basically three categories of cocktails at restaurants (completely excluding DTD and Epcot at the moment):
A) A non-signature restaurant that serves cocktails. The selection is generally relatively slim, if not just completely taken off of the Big Book I'll mention in point B. Take, say, the Trail's End: lovely cheap little place with great food, but all they have is stuff from the Big Book. Two non-signature restaurants that do have some unique selections are 50's Prime Time and the Wave, but even they fall back on the 'Light Up Glow Cube Magical' lemonade/healthy drink. This is where the Epcot exception comes in to play: most of them say 'Eff that'. Tutto Italia/Tutto Gusto will serve traditional and not so traditional Italian cocktails, the two Mexican restaurants and the Cave will have excellent margaritas (if they aren't being premixed), both restaurants in Japan have a good selection of sake cocktails, the Rose and Crown does some mixes with beer if you want to count that as a cocktail, and Spice Road has... okay, Spice Road has weird drinks that have nothing to do with Morocco, but at least they're not the same as everywhere else. Though not as helpful for you looking for cocktails, Sanaa deserves a mention, too: while they only have three or so unique cocktails, they have a ton of unique African wines by the glass- some that you can't even get over at Jiko or Boma (at least not by the glass). Oh, and Yak and Yeti in Animal Kingdom has their own cocktail list, which tend towards the light, refreshing, but not really boozy catagory.
B) The lounges, which is where the Big Book comes in to play. It's a large bound brown faux-leather book that describes all of Disney's 'signature' cocktails. This where you find the Magical Star cocktail. Not everything on these menu's is bad (I do like the Smoked Turkey, myself), though the wine list is hideous. Almost every lounge serves this menu. There are a few exceptions, and honestly, they can be hard to figure out. The Victoria Falls lounge over at the Animal Kingdom Lodge serves most of the specialty cocktails you could get at Jiko's as well, while the Territory Lounge at Wilderness Lodge won't even let you have a glass of the northwestern wine Artist Point is so known for. Minzer's Lounge at the Grand Floridian is one of the lounges that stubbornly refuse to follow this, and has their own bar menu (though I'm guessing they can make you anything on the Big Book), serving some items from Citrico's and some items they're known for. The Brown Derby's Lounge in MGM/DHS serves their own menu as well, usually of classic cocktails. The upstairs lounge at the Polynesian that's name is currently escaping me has their signature drinks there, in paticular the Lapu Lapu (out of a pineapple) and the Backscratcher.
C) The signature restaurants, as a rule, have their completely own bar menu, and often don't know/don't care to make anything from the Big Book (though with a full bar, they'll certainly try to make whatever you like). This is a 'depending on your tastes' thing: Jiko's cocktails, for instance, try to use at least one African liquor in them, which is pretty darn awesome, but they also tend towards the sweet side. I agree that Bluezoo has one of the most interesting cocktail menus ever, and love it. California Grill's cocktails, I enjoy. I do like the Brown Derby's classics (same as they have at the lounge, basically). Flying Fish has this frozen peanut butter and ice cream dessert drink that is super sweet and gives you brainfreeze, but is so delicious all the same (yet so filling).
Then, there's the other exclusion- the DTD restaurants. They aren't owned by Disney. They do whatever they want, and don't touch that Big Book.
Raglan Road has some interesting cocktails: I like the sangria made with hard cider. Paradiso specializes mostly in frozen margaritas and sangrias, sometimes whirled together, sometimes in huge cups (also, a lot of tequila). The Boathouse has a very small cocktail menu (but a full bar), but everything I tried there was good. T-Rex and Rainforest Cafe will serve you huge drinks with little booze that still are extremely refreshing; not really my thing, but there. Portabello's was trying a lot of wine cocktails for a while, but I haven't been there in quite some time, so I'm not sure what their focus is now.
Coupled on to all of this is new arrival Trader Sam's, which is basically a full bar with it's own deal. They specialize in rum drinks: I think there's one drink with vodka and one with tequila, and the rest is rum. Fun drinks, though. Make sure to ask about prices and not buy the glass unless you want it: almost all drinks you can get them with the glass or without.
So to summarize: for interesting cocktails, you want Epcot World Showcase restaurants or DTD restaurants when it comes to non-signatures (or, basically, any restaurant not owned by Disney). For lounges, you want Minzers and the Brown Derby Lounge for totally unique menus, and Trader Sam's as a full bar, with a few other lounges having a few unique items: the four lounges/bars in Epcot (La Cava, Tutto Gusto, Spice Road, and Rose and Crown) also have their unique stuff. For signatures, anywhere is good, but Bluezoo is better then good.
