The Big Bang Theory Season 3 Episode 23 (The Big Bang Theory s03e23) with title “The Lunar Excitation” airs on Monday, May 24th 2010 at 09:30 pm via CBS.
Here is summary for The Big Bang Theory Season 3 Episode 23 :

While Penny worries that dating Leonard has ruined her for normal guys, Wolowitz and also Koothrappali search for Sheldon’s perfect match online.

Few hours after original series aired on TV, online streaming video for The Big Bang Theory Season 3 Episode 23 usually available on Net and of course, if video available, as soon as possible will show you where you can watch this episode for free.