Depends on previous training, race course and race effort. E.g. if the course had a lot of downhills, it takes longer to to recover.
I've found that if I ran negative splits and finished strong, I recover faster than when I ran heavy positive splits and finished just "hanging on". I've also found active recovery is best for me. I generally don't run for about 5 days after a marathon, but I do some easy swimming, cycling and elliptical in the days right after a marathon. If I just sit around, it's like my body shifts in shutdown mode.
Four weeks ago, I ran the Erie marathon - I did a two week reverse taper. On the second weekend, I ran 15 at faster than my Erie race pace. I could feel the deep damage late in the run, but I felt GREAT. I couldn't believe it. Then I did a two week taper and ran another marathon. I ran 4 minutes faster on a much harder course.