Concept2 Indoor Rower
Concept2 is a company with perfect profile and cool history. I have been riding models B, C, D and E of their basically indestructible machines.
Prior Velvet revolution I was even erging on bad copies of model B from the Eastern bloc :-Z
The most interesting alternatives I found are WaterRower (check James Stroud comparison) and RowPerfect. Both are not (that) bad, but I decided to bet on Concept2 as I know it for a very long time; because of the community (log, ranking, challenges, BIRC/CRASH B, ...), old models support (Concept2 supports even oldest models up today) and use of Concept2 by majority of elite rowers.
General consensus is that model D/PM3 is perfect fit for home use, while model E is kind of "Rolls-Royce" meant rather for fitness centers and hotels. Model E is bigger, higher, nicer and ultimately durable. So, after not much deliberation, I decided to invest in my health and became happy owner of Model E/PM4.
You may want to check model D/E comparison and PM3/PM4 monitors comparison.
There is a lot of accessories and gadgets - log card allowing you to track all your workouts (I had it in the past while erging in fitness centers around Prague), CBreeze (the perfect accessory with the best 'value for price' ratio), RowPro (for social rowers), ErgLog (Android phones), KinoMap (to row your favorite river/trail), slides, ShoxBox ... and much more.
Before you start erging check the technique and common errors videos. Set the damper (which has the similar function like bike gearing) to 5 (not to 10 - which is the most common beginner error) and experiment from there. Learn about drag factor (allows you to set different machines to the same resistance e.g. older machines have typically lower resistance with the same damper settings). Join a forum and find a training plan like C2 Interactive, Pete's plan or Wolverine plan. I also found very useful French Rowing Federation 2k Strategy and pace calculator.
I follow Concept 2 2k interactive plan 4 days a week with 2 extra sessions of rowing or running and aiming to get to 300km/month+ (again ;-).