I'd hate to dissapoint, but the World Showcase beer selection is pretty pathetic when you think about the type of offerings they could have. I think a few years back, WDW signed a contract with mega-brewer InBev, so most of the kiosks now only serve typical import beer you can find throughout the US.
It's still worth checking out Germany, as they probably still have Spaten Optimator and Franzikaner on tap. The Rose and Crown should have Bass and Boddington's, and maybe New Castle Brown? You can also grab a Dos Equis in Mexico.
The best beer in all of WDW is served at Le Cellier, but you'll need a reservation to get to it. They should still be serving the Unibroue Canadian-belgians. If you happen to eat at LC, I'd strongly reccomend the Fin Du Monde and Maudite.