Twenty companies are finalists in this year's Medium (100-249 employees) category of the Phoenix Business Journal's Best Places to Work awards program. The winner, and complete category ranking, will be announced Dec. 4 at a special awards luncheon at the DoubleTree Resort in Scottsdale. There are a total of five categories based on number of employees, from Micro (up to 49) to Extra-Large (1,000-plus). Click above to see a slideshow of all 20 Medium category finalists. Companies nominate themselves…