BestBuy has Big Bang Theory Season 1-3 on DVD for a geektastic $16.99 each plus free shipping. Sales tax applies nearly everywhere.

Season 1
University physicists Leonard and Sheldon know whether to use an integral or a differential to solve the area under a curve. But they don’t have a clue about girls. Or dating. Or clothes. Or parties. Or having fun. Or, basically, life. So when a pretty blonde named Penny moves in the apartment across the hall, the guys decide to get an education outside of the classroom. Boys, you have a lot to learn. With series creators Chuck Lorre (“Two and a Half Men“) and Bill Prady (“The Gilmore Girls“) concocting the right mix of logic and lunacy and stars Johnny Galecki (“Roseanne“) and Jim Parsons (“Judging Amy“) turning geekdom into Phi Beta fun, “The Big Bang Theory” is big on laughs. And life.
Season 2
The science of funny is back! At work, physicists Leonard and Sheldon and their geek pals conquer the cosmos. At home, real life from dating to driving conquers them. This season, Leonard gets a girl. So does Sheldon. (Sheldon?!) Howard drives the Mars Rover into a ditch. Raj woos a terminator. Gorgeous girl-next-door Penny falls under the spell of Age of Conan. And super-smart, überconfident Leslie Winkle reduces mere men to spineless jellyfish. Twenty-three laugh-filled episodes from series creators Chuck Lorre (Two and a Half Men) and Bill Prady (Dharma & Greg) and a talented cast with astronomical comedy I.Q.s show why Big Bang is such a big hit.
Season 3
Worlds collide in Season 3! A love affair with Penny has opened a big, wide, wonderful world of romance for Leonard. But Sheldon likes the world just the way it was, thank you. All of which makes for a zany comic triangle with brainy, clueless Sheldon and practical, grounded Penny hilariously vying for the role of hypotenuse. This complete 3-Disc, 23-Episode Season 3 Set also features Raj, Howard, tattoos, football, awkward dates, jail time, Stan Lee, a The Lord of the Rings ring and all the fun of a series that only gets better. The Big Bang Theory “has transformed from a cute comedy about eggheads and their hottie neighbor into an addictive ensemble piece that could be this decade’s answer to Friends” (Lynette Rice, Entertainment Weekly).