As with the first season, I purchased the second and third at BMV as DVDs - although the price rose from $5 to $6. Evidently the world is saturated with discarded copies of the early seasons - everybody who wants to watch it has done so by now.
The second season isn't as funny overall as the first, but has a couple of the series greatest comedic moments. As I mentioned in the review of the first season, the funniest moment they ever managed to put on film was the Leonard Nimoy napkin (in this season, "The Bath Item Gift Hypothesis"). I'm also fond of Rock-Paper-Scissors-Lizard-Spock ("The Lizard-Spock Expansion"). Another stand-out for me was "The Maternal Capacitance:" while Leonard's mother Beverly (Christine Baranski) is too cold and analytical for me to find her entirely believable, she does deliver some of the show's best lines. Her take-down of Howard and Raj at lunch is brilliant: "That's fascinating. Selective mutism is quite rare. On the other hand, a Jewish male living with his mother is so common it borders on sociological cliché. You know, both selective mutism and an inability to separate from one's mother could be due to a pathological fear of women. That's would explain why the two of you have created an ersatz homosexual marriage to satisfy your need for intimacy."