Try a multisport race.
This off-road triathlon through Michigan farm country includes a half-mile swim, a 12.5-mile mountain-bike ride, and a 3.4-mile run. Afterward, hit up the thriving brewpub scene in nearby Grand Rapids.
There may not be a better triathlon venue in the U.S. than the rolling coastal flats in Freeport, Maine, but the best part of this race is the after-party lobster bake, where you can gorge on fresh lobster, steamers, and plenty of local microbrews.
One of the newest endurance events is a brutal Swedish invention called Ötillö Swimrun. Ötillö is a play on the Swedish phrase "island to island," and the race is exactly what it sounds like: Swim from one island to the next, run across the land. Courses are generally 75k (65k of running, 10k of swimming); a shorter race is offered the day after.