Ed Whitlock. He's a 73-year-old man. Last year he became the first person over the age of 70 to run a marathon under 3hrs. Here is how he trains:
Essentially no speedwork, except before a race. Then maybe for 2 or 3 days. He won't do a longer run, but instead a shorter run, and quicker. He doesn't do any real interval training or speed training. Mostly a run around the cemetery close to his house. It's about 1/4 mile around. He'll do that for 3 hours, about 4 times a week. He has done 7 days of that at times.
You can read more about it here:
http://www.runnersworld.com/cda/daily_news/0,,s6-0-0-0-0,00.html#whitlock