Well, I come from an uber intense cross country background (80+ miles a week) with an emphasis on competition so this really isn't applicable...but anyway...
You need to have a least one, if not two days of rest, and you need to have some variance in your running from there. Otherwise you are going to platea and not see any returns after a while.
It would go something like this -
Day 1: Long rung
Day 2: Easy day, short distance, slow pace
Day 3: Uptempo run or interval training of some sort
Day 4: Normal training run at about 55-60% heart rate
Day 5 Normal training run at 55-60% of heart rate
Day 6: race/intensity workout - intervals/ladders/distance sprints/uptempo run at 80% max heart rate
Day 7: easy recovery day
That's overkill for somebody just looking for fitness, I know, but the idea is that you need rest in there somewhere. Not only your body, but your mind will burn out doing the same thing day, after day, after day, after day. Throw in some biking, or swimming, or rowing in there every now and then to mix it up.