General fact: 306 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 306 is the number of 5-digit triangular numbers.
Trivia: 306 is an uninteresting number.
Historical date: November 1st is the day in 1611 that William Shakespeare's romantic comedy The Tempest is presented for the first time, at Whitehall Palace in London.