Newsletters based around political observation with articles on debated topics or interviews with politicians can appeal to audiences who take their politics seriously. Use special editions of your newsletter around election time to keep readers up to date on bills and other issues they need to know before going to the polls.
Financial topics are always good for newsletters. People want to know how to manage their money and how to make more of it. Newsletters that address topics related to finance can include stock market information, interviews with financial advisers, and reviews and articles addressing many of the get-rich-quick programs on the market.
Food topics always can make for mouth-watering newsletters. Covering famous chefs can be great material for food newsletters, as can including personal recipes, reader-submitted recipes, or a recipe of the month.
Company newsletters offer the opportunity to keep employees informed about upcoming events as well as job openings within a company. Employee of the month, job offerings, and information regarding the company's plans for the future are topics an employer newsletter can include.