Spirits, wine and beers are all plant-based, however beer and wine are sometimes processed using animal by-products (egg, gelatin, casein, glycerin, or isinglass) used as a fining agent for settling out suspended matter in the vat.
Generally, British beers use isinglass, gelatin, glycerin or casein. German and Belgium beers using traditional methods of brewing are vegan.
Barnivore.com has an amazing database of beer brands labeling which are vegan, mostly vegan and not vegan: http://www.barnivore.com/beer