Rowing Canada – How to Use the Indoor Rower
http://rowingcanada.org/sites/default/files/pdf/rcaindoorrowposter.pdf
The Concept 2 website (that’s a popular erg) has lots of information about indoor training.
This is a good starter video:
http://www.concept2.com/indoor-rowers/training/technique-videos
A great list of workouts:
http://www.concept2.com/files/pdf/us/training/Training_24Workouts.pdf
You can sign up to receive workouts of the day via email:
http://www.concept2.com/indoor-rowers/training/wod