Just in case you've forgotten, an outbound link is a url that you have on your site that points to another website.
In today's Google PR obsessed Internet world, everyone is completely focusing on getting in bound links to your site. While you should always be on a mission to get more sites to link to yours, you must not forget their polar opposites.
Remember, by having outbound links from your site, you are in essence "voting" for site you link to. This is part of entire ranking algorithm process for all search engines. The idea is, that if two sites are similar in content and design, a site with more links pointing to it would be considered more important by search engine.
So then, why should you help out any other site? Actually, by carefully linking to other relevant sites, you are increasing relevancy of your own site.
Pretend I have a pizza shop, and I am located in Anywhere, USA. It's a typical site that displays types of pizza, store location, hours, and coupons. I also know power of outbound linking. For this case, I am going to link to 10 sites: Domino's, Pizza Hut, Little Ceaserís & Papa Johns. Next, I link to 6 sites that are physically located in Anywhere, USA. (And their physical addresses are listed on their sites.)
Now, I will switch roles and view site as a search engine spider. I navigate through site, and determine that this site is about pizza. Then I find a resource page and discover some well-known links (Domino's, Pizza Hut, Little Ceaserís & Papa Johns - and as spider I know that these are major players in realm of pizza). Next, I find 6 links to sites located in Anywhere, USA.
So, as a happy spider leaving site, I now know that site I just visited is about pizza (site content and links to major players of pizza industry), and that it is located in Anywhere, USA.