For any website interested in making people do something such as buy a product or donate money to a cause one of the most important things to work into your home pages is action links. Actions links are clearly labeled and explained links that link someone directly to a website where they can go about making that action.
For instance if you wanted someone to Donate money to cause you should have at least one link if not two on your main site that will direct someone to a page where they can fill in the information required for the donation.
Creating actions that are readily available and easy to understand encourages people to take them and increases that chance they will do so. Actions links do not half to be large things but they should be simple and logically with regards to everything else on your homepage.
Remember people are lazy they are unlikely to look around for a way to do something on your website so if you want it done you had better make it easy for them.