26.22 Miles (26 miles 385 yards)
Record a/o Dec. 2013:
Men 2h03:23 (4:42/mi)- Wilson Kipsang, Keyna
  7 of the top 10 times were by Kenyans
Women: 2h15:25 - Paula Radcliffe, GB

Qualifying times for Boston Marathon (18-34 age bracket):
Men   3:10:59 (3 hours and 10 minutes) ( 7:17 min./mile)
Women 3:40:59 (3 hours and 40 minutes) 
An exception to the qualification requirement is awarded to 1,250 runners who
raise a pre-determined level of sponsorship for officially designated local charities.

Equivalent pace (av. mile times)
2:11   -  5    min/mi
3  hr  -  6:51 min:sec/mi
3.5 hr -  8    min/mi
4 hr   -  9:09 min/mi
4.5 hr - 10:18 min/mi
5 hr   - 11:26 min/mi

California International Marathon (CIM)
Coverage at KCRA Channel 3
CIM 2008 Results (fastest by division [age group])

Men					Women
Div	num	top	median	90%		num	top	median	90%
19UND	33	3:15	4:04			20	3:30	5:03
20-24	111	2:28	3:57	5:03		146	2:39	3:58	5:03
25-29	268	2:17	3:39	4:45		300	2:32	4:09	5:14
30-34	400	2:17	3:38	4:44		355	2:37	4:10	5:21
35-39	528	2:27	3:42	4:50		380	2:44	4:14	5:20
40-44	530	2:30	3:45	4:48		366	2:41	4:13	5:04
45-49	466	2:37	3:50	4:54		311	2:53	4:18	5:17
50-54	327	2:47	3:57	4:57		186	3:18	4:17	5:23
55-59	197	2:48	4:06	5:13		73	3:52	4:47	5:59
60-64	100	2:51	4:13	5:08		28	3:31	4:40	5:51
65-69	31	3:17	4:17	5:57		14	3:51	5:09	5:44
75-79	5	4:17	5:17	5:30
Total	3011	2:17	3:51			2185	2:32	4:16

90% - 90% of times were this or less.
Sample size was small with 14 women in the 65-69 group and 14 men in the 70-74 group.
Source: www.runcim.org/data/08Results.html

Note: According to a NY Times Article "Plodders Have a Place, but Is It in a Marathon?" "In 1980, the median finishing time for male runners in United States marathons was 3:32, a pace of about eight minutes per mile. In 2008, the median finishing time was 4:16, a pace of 9:46."
Note: The CIM is mainly downhill and gets a lot of runners trying to establish good qualifying times for the big races.

Some observations:
Women's times generally get better after those big birthdays, 40, 50 & 60.
Women peak earlier (20-24) than men (25-29) and drop off earlier (55-59) than men (70-74). This is a generalization, Paula Radcliffe set the worlds record at the age of 30 and Grete Waitz won her 9th New York marathon and Radcliffe her 3rd, both at the age of 35.

  Men 30-39 (a smoother distribution).
One sigma (standard deviation) is 45 min.
(I don't know how to calculate the upper limit for a gamma distribution [are race times gamma?] but it is something greater than 4:24)

Run-Walk Strategy:
Many beginning and intermediate runners use a run-walk strategy instead of running the whole distance. This works for any distance running from a 5K up.

See Run-Walk

More no-shows than DNFs at New York Marathon:
Of the 60,000 people who qualify and register for the New York Marithon, 15,000 are no-shows, 2,000 do not finish.
Most cancel because of injuries while training or not meeting training goals.
Tips in the article below:

• Have a complete exercise program including upper body to avoid things like back problems.
• Build up slowly, 6 mos. is better than 2 mos.  Long runs should include a 20 miler (or more) and two 18 milers spaced two weeks apart.
• Taper 3 weeks prior to the race. No run should exceed 12 miles two weeks out with only two or three runs of two to four miles the last week.

American Marathon drought:
The days of the days of Salazar, Beardsley, and Rodgers are long gone. The last American to win the Boston Marathon was Grey Meyer in 1983. Americans are lagging behind rivals from many other countries, including Japan, Mexico, Australia and African nations like Kenya, Ethiopia and Tanzania.
Ryan Hall, with a 2:08:24 in his debut Marathon in 2007 and tenth in the Olympic marathon in Beijing, will run in 2009.

Pre-Race Prep:
Food:

See pre-race for 5K

Warm Up:
See Warm-up in 5K

Gear:
Compression shorts are claimed to reduce fatigue.
Enough people believed these claims to make sales of compression gear jump 170 percent from 2008 to 2010, giving it a 5 percent share of the sports apparel market, according to a recent consumer-research report.

You can spend anywhere from $30 to $100 for CEP Dynamic+ Run Shorts
Adds say thing like "Proven Compression Technology - Promotes faster muscle recovery & blood circulation, & minimizes injury." "fatigue reducing".

However the first two articles that came up in google (see below) were skeptical.
They were reviewing shorts; Tights deliver graduated pressure, meaning garments are tighter around the ankle than the knee, which helps improve circulation from the lower leg.
I can see where this would be an advantage.

Jeremy Repanich, a Brooklyn-based writer says at deadspin.com - What compression gear will and wont mostly wont do for you.
"I kept track of my own running times, with and without tights, and that data led me to the same conclusion as the scientists: If you're looking for better endurance or more speed, don't bother with compression gear. It makes no difference."

CEP Compression Shorts Review | No Meat Athlete agreed.
"So much of distance running is about comfort and being able to relax, and I found that having my thighs squeezed like vegan sausages made that tough."

A rule of thumb is, dress like it's 20 degrees warmer than the actual temperature.

Links:
Running USA's Annual Marathon Report | Running USA
Virgin London Marathon statistics | foot4ward
USA Track & Field (USATF)
www.MarathonGuide.com
Marathon at wikipedia Training:
MarathonTraining.com
www.MarathonRookie.com/
Marathon Training: RunnersWorld.com
Marathon-training.net
Do You Make These Four Tapering Mistakes? | Runner's World
5 Running Tweaks That Took an Hour Off My Marathon Time - Life by DailyBurn