Many Non-Profits have a hard time establishing a consistently visited web presence. There are many attributes that contribute to this but perhaps the most important is the relation of different content types (i.e. - Video, Blog Posts, Articles, Research, etc).
Most people when visiting a website whether direct or through search already know what they are looking for. In that process they want as much content pertaining to their inquiry and your ability to deliver will decide how often they return to your website. This is particularly true when your non-profit is focused in a much defined mission such as breast cancer, military topics, or the construction industry as a few examples.