Bring a pot of salted water to a boil. Prepare a large bowl of ice water and set it by the pot. Working in batches, boil the broccoli rabe for a minute or two until bright green. Using tongs, remove the rabe from the pot and place in the ice water to stop the cooking. Once all the rabe is cool, pour the rabe into a colander and set aside.
Toast the pine nuts in a small, nonstick saute pan over medium heat for 3 to 4 minutes, stirring constantly, or until evenly browned (it will smell like popcorn). Take care not to burn them–they cook quickly! Dump the pine nuts into a bowl to stop cooking.
In a large frying pan, heat the olive oil over medium-high heat. Add the garlic and red pepper flakes and cook for one minute or until fragrant (but not brown). Add the broccoli rabe and cook, stirring constantly, for 3 to 4 minutes or until tender-crisp. Add the raisins and the pine nuts and toss to combine. Season with salt and pepper to taste.
If you want, add a dash of Balsamic vinegar or a squeeze of lemon at the end. This is delicious with grilled salmon, pork tenderloin, or meatballs with tomato sauce. Definitely one of my favorite easy vegetable side dishes!