Writing a widget for Opera or an extension for Firefox might be worth looking into for your website. If you have a forum, it might check new posts or new PMs. If you have a current events website, you might have a calendar.
Looking through the available widgets, quite a few sites have started their own widgets. I reckon that if you have a site with a reasonably technical audience (who are more likely to use Opera) as well as having frequently-changing content, then a widget could be a great resource and promotional tool.