Your visitors will appreciate if you link to some related sites / information. And in my opinion Google will see this positively.
While it sounds logical at first glance, you're wrong. Ask who ever famous SEO and they will tell you related outbound links in place will help your site. Internet is all about linking. Google certainly know that.
In a sense, it makes your website a website. since google likes sites to llok natural and created for people not for SE's but you can always use nofollow attribute
External Links don't have much of an effect on your own page. However do not link to bad neighbourhoods otherwise this will act as negative points for your site. By Bad neighbourhoods this means linking to external sites that break the rules in some form or another. External links also reduces your sites potential PR Juice, for every external link you place you are losing the PR juice you can offer to potential advertisers. However obviously adding rel="nofollow" preserves this link juice that you can offer to potential advertisers.
Out bound links will not help at all when it comes to SEO. If it helped, then everyone will start to put links like google.com, yahoo.com on every page of your site. Try to limit the number of out bound links in your site. Try to get in bound links, that is backlinks. This is the important thing.
as more external link, more popular will be the site, so google will think the site is known for everybody, so.. that site will be high rank!