Most insurance policies remain in effect on track days as well. I read my whole policy and it said that as long as it wasn't a timed, competitive event you were covered. Since most track days are high performance driving SCHOOLS with instructors, it wouldn't apply. But yeah if you're in a racing club, just get track insurance.
Another fun part of my policy: In the bodily injury and comprehensive coverage exclusions section, it says that coverage does not extend to loss caused by "discharge of a nuclear weapon, even if accidental." Who said fine print couldn't be entertaining?