Make your website content pay you
Unless you're running a highly corporate website, something you should be doing as a matter of course is including Google Adverts into your webpages, using AdSense.
Adsense works by 'reading' the content of the page it's displayed on, and then fetching adverts relevant to keywords found within your copy. On the odd time there are no adverts to display, you can choose to either show a Public Announcement advert (recently a banner ad asking for support and aid for the victims of Hurricane Katrina). or you can tell it to display an ad of your choice.