Sun Tues Wed Fri
Week 1: 7 mi 6 mi, incl 4 @ T 6 mi 12 mi
Week 2: 7 mi 6 mi, incl 2x1600 7 mi 14 mi
Week 3: 7 mi 7 mi, incl 5 @ T 6 mi 16 mi
Week 4: 7 mi 8 mi, incl 6 @ T 6 mi 18 mi
Week 5: 7 mi 7 mi, incl 3x1600 7 mi 20 mi
Week 6: 7 mi 8 mi 8 mi 8 mi
Week 7: 9 mi 9 mi, incl 7 @T 9 mi 16 mi
Week 8: 10 mi 10 mi, incl 8 @ T 8 mi 20 mi
Week 9: 8 mi 10 mi, incl 4x1600 11 mi 16 mi
Week 10: 12 mi 10 mi, incl 7 @ T 10 mi 20 mi
Week 11: 11 mi 7 mi, incl 5 @ T 6 mi 8 mi
Week 12: 6 mi 3 mi 6 mi, incl 4 @ T 3 mi
Week 13: Race Day!
The above is the training plan I have been using ever since the San Francisco Marathon 2009. It was generated by Runner's World Smart Coach (though they have since changed their plans because I can't get it to generate this exact plan again with the same inputs).
Quick explanations: T = tempo runs. The 1600m repeat intervals always have a 800m recovery jog in between each pick-up. I generally do the speed work smack dab in the middle of the mileage so that I have equal warm-up and cool-down periods. The specified pace for every other run is always "easy." I never do any other aerobic activity on the other days of the week (I'm trying to change this but I hate to exercise).
I've PR'd 4 times on this plan every time I've used it. While not for everyone, I think that my body does best on less running days and higher mileage per day. This plan peaks out at 52 miles/week which is about what I used to peak at on a 5 day a week plan. I love how it gets you running 10-12 miles and it doesn't feel like a "longer" run at all. If you want to run 26.2 fast, I don't think 10-12 miles should feel very long to you. This plan will get you running 10 miles and feeling like it is any other run day. The two week taper vs. the more popular three week taper seems to work better for me, too. I have a very low natural athletic ability (I recently took 6 days off and could tell my cardio had suffered for it) and I think it is better to keep my mileage up as long as possible.
I've been trying to grow within this plan the last two cycles, especially. I've been adding in hill work, fartleks, and marathon-pace miles here and there. I've been debating about folding in a fifth day of running. But with my leg tweaks I want to concentrate on just the extra little speed play here and there for now. My goal maybe the next training cycle or one after is to up the overall mileage a tiny bit.