You've won an award, you've held a brilliant event, you've secured a new contract. Share your news with your visitors and you can big yourself up, all in the name of being sociable. Add pictures to your news stories and you're opening up your organisation, giving it a face. You show yourself as a business worth engaging with, a service great to use.
But whatever you do, keep your news up to date. If your latest item is pictures from the charity gala circa 2011 then you're clients will think either a) you don't care about your site or b) you've had a very quiet few years. And no, they won't think you must be doing so well that you're too busy to update the website.