Dipsea Race (Marin County, CA)
While big city marathons have become international events, the Dipsea allows racers to get a piece of local Northern California culture. For one thing, the application process for the 1,500 spots, which was still done by snail mail through 2012, favors locals. Then there's the handicapping system, which evens the playing field for competitors by giving head starts based on a set of data (age, gender, so on) compiled and interpreted by a guy known as "Birdman."
Once you're in the race, it's 7.4 beautiful and challenging miles from Mill Valley to Stinson Beach, including 50 stories of stairs right at the beginning, single-track trails, a plank footbridge, switchbacks, lush forest, and ultimately a beach where you can cool off. There are a few shortcuts if you know where to look. [Second Sunday in June; dipsea.org]