Broccoli Rabe (pronounced "rob") is a member of the Cabbage or Brassica family. Broccoli rabe is a variety of broccoli that has smaller heads and a pleasantly bitter flavor.  Also called rabe or rapini it
offers other qualities besides its tender texture and intriguing but pleasantly bitter flavor. It’s a nutritional powerhouse. Not only is it rich in beta-carotene, vitamin C and potassium, it’s also an excellent source of
folic acid - a B vitamin that is important for good cardiovascular health. Recent studies have found that men and women who don’t get enough folic acid in their diets have a greater increased risk of fatal heart disease. This vitamin is also vital for a healthy pregnancy. 

Here is a nice site to a Broccoli Rabe recipe:

http://www.lifetimetv.com/recipes/frameset.shtml/brabe.html