There are several different popular brands that depend on your price range.
Drug Store: L'Oreal, Maybelline, Cover Girl, Wet n Wild, Revlon, Neutrogena, Almay-those are some of the basic popular lines you would find at any store. These carry products priced lower but are often just as good as their expensive counterparts.
Consultants: There are personal consultants who sell for Mary Kay and Avon and several readers enjoy those makeup lines.
Makeup Counter/Sephora/Ulta: There are too many to name, but the most popular include Stila, Dior, Smashbox, Make Up For Ever, Chanel, Clinique, Benefit, Urban Decay, Tarte, Laura Mercier and Estee Lauderdale, off the top of my head.. these are more pricey.