Like how inbound links are important to your site the outbound links are also important which influence search engine rankings. Links to other web pages tell search engines that your site can be trusted and there is nothing to hide in your site. These outbound links should not be used to the sites with negative information. Outbound links also creates back links to your site. If your outbound link links a web page where a link to your page is placed that also gives good results. But you should not use many back links to your site.
If you link to high quality sites with good page rank, search engines associates your page with the pages of those sites. If you have not good outbound links your visitor may go back to search engine which will also give negative effect.
Never have out bound links to the spammers which might effect to a ban of your site by search engines from their search results.