For beginner rowers (and even not-so-beginner rowers), take a look at this short video from Concept II.
Olympic gold medalist Imogen Grant explains the rowing stroke.
Download and study this one page poster from British Rowing - The Perfect Stroke. A lot of what you need to know is obvious just by looking at the pictures.
This video of Olympic gold medalist Zac Purchase is what we should all aspire to!
This more advanced video by World Champion John Dunn (from Calm Waters Rowing) nicely summarises the whole rowing stroke, and explains why David Crawshay and Scott Brennan won the gold medal at the Beijing Olympics in 2008.
For a day when bad weather cancels rowing, you can watch this series of eight videos (1 hour 40 minutes in total) by GB coach Robin Williams, in his back garden, talking about rowing - what's not to like?