There is a natural human belief that if some is good, more is better. This idea is all too often false, and can very destructive with training. It is important to realize that running does not make you a better runner - it is the rest that follows running that makes you a better runner. So the key to effective training is to balance the training with the rest.
I have tried many different patterns of training and rest. I have found the most effective pattern for me is to run four days a week. These four days are all 'quality days'; I run for three hours Monday, Wednesday and Friday, then run four hours on Saturday. This gives me lots of long running, with enough rest to support that mileage.
The key to running four days a week is that every run is a quality run that requires rest to recover. I don’t run four days a week as a 'minimum I can get by' approach. This is being prepared to push the boundaries of my physical capabilities. I don't take extra days off to make things easier - I do it to make things harder. Running four days a week enables me to train on those four days much, much harder than I could if I trained more frequently. Currently I am focused purely on distance, but I have found the same thing when I am focused on speed as well; three interval training sessions and a long run works great.
My Friday/Saturday runs are the only time I run consecutive days. The idea is that I have not fully recovered from Friday when I do the Saturday run, so I am doing my longest run on tired legs. I do this because I cannot afford the time that it would take to run the distances that would otherwise be required. I consider Friday/Saturday to be a single training unit, though not as effective as the mileage would be if I could do it on a single day.
Running four days a week is tough. It is tough to run hard enough to need the 48 hours recovery. But it is also physiologically tough; taking three days off is not as easy as it seems. The feeling that I am not doing enough, or that my fitness will dissipate in 24 hours is corrosive. I find it hard not to do a trivial run on Tuesdays and Thursdays, but I do these trivial runs for psychological reasons. It's not the right thing to do, but we all have to battle our demons in our own way. (I am trying to give them up, honest!)
There are exceptions to this advice. If your running training is not hard enough to require 48 hours recovery, you will be better off running more often. If you are just starting to run, then running 5-6 days a week may work for you. If you are running for general fitness and not pushing your body to its limits, then running 5-6 days a week may work for you. If you are have DOMS, such as after a long race, more frequent runs may help. (I’ll write more on DOMS in a later entry.) However, I would always advise one full days rest each week.
Am I alone in my suggestion, or are there other plans that support the idea? Hal Higdon's Advanced II Marathon plan (http://www.halhigdon.com/marathon/advanced2/advancedII.htm) has 6 days of running, but two days are trivial. Jeff Galloway (http://www.jeffgalloway.com/training/marathon.html) uses four days/week. The Runner's World beginners plan (http://www.runnersworld.com/article/0,7120,s6-238-244--6946-2-3X5X7-4,00.html) is four days/week. (The RW intermediary & advanced are 5 days.) Jack Daniels (my favorite coach) defines just two work outs a week, and leaves it up to you how you fit in the other miles.
What about 'active recovery'? I've only found one scientific study [1, 2] and that indicates that active recovery does nothing to help. On the other hand, it does not indicate that active recovery does any damage either.
I have included few supporting references or scientific studies around training plans. There does not seem to be any evidence to support any given plan over another plan, just anecdotal experience (of which this is part.)
 Neuromuscular fatigue and recovery in elite female soccer: effects of active recovery.
 Rest v Active Recovery