It's likely not to be representative, but my experiments in this directions with links to dmoz, wikipedia, digg and so on over 3 month didn't have any effect at all.
I think for an unknown, new website to link to high quality websites like CNN or NPR or NYT is a good idea since many people believe that websites that link like that gain trust. I do not have any evidence that it will benefit you directly but as you build your own content gradually, a high trust website will do better than one that links to other spammy websites.
It can finetune the overall relevancy and link profile of the pages... by bringing them closer to what the ever current standard of a 'trusted' resource looks like. This however is different for each theme and topic.
For example, an informative page would probably gain from outbound links to academic resources that are relevant ( or which it quoted from, used as reference, whatever, as this *IS* the norm for both on and offline publications that can be taken seriously ). Regarldess of the size/authority status of the targets of the links, if they're relevant, and the link would do good for the users...
... you can assume that Google already knows that this is common practice - or perhaps even 'expected' - among non-spam/trusted sites on the topic ( at least it probably already has such behavior recorded during its analysis of some 'ideal' pages ).
But I can't imagine that linking out to Wikipedia would do anything at all for ecommerce or retail sites. And since they ain't linking out, never have... , Google probably doesn't have such expectations either, and basically doesn't care.
It's about how close your site resembles to resources considered aithoritative. Varies by theme / topic.
[edited by: Miamacs at 5:40 pm (utc) on Oct. 12, 2007]
I add links to relevant pages when it makes sense, because it makes sense. There are no other considerations.
IIRC the theory was anchor text "counted' for both the linking and linked-to page, so it made sense to have some on topic outgoing links.
May well still be relevant.....
Linking to other relevant information through hypertext is surely what the internet is all about? It allows you to refer visitors to other sites to clarify and explain terms or ideas that you do not have the time or space to address.
Any seo advantage? I haven't found evidence either way, but I know that when "surfing" I really appreciate a page that has sensible links embedded in the text that help me understand what I'm looking at, or lead me off on related trains of thought...
Any site that didn't include at least some links in their text would be missing something imho.
My rule of thumb for linking out is "will this link enhance my users' experience in some way?" and if the answer is yes, then I add the link, and if it is no, then I don't. And that's the only consideration I give it.
Two core Google Search concepts, PageRank and TrustRank, depend on linking for their very existence. So it stands to reason that Google would look favorably on legitimate, relevant outbound links.
Linking out naturally to sites is just a component of a natural link profile. If you reciprocal link all over the place and add a few links to dmoz to rank higher, that isn't going to fool Google.
Your primary focus whenever you ask questions like this is "how is this going to improve the usability/content of my website? how is this going to make my site more valuable to users?"
Follow that line of thinking and it will translate to higher search traffic.
Outward links to relevant sites are good and I continue to do them and enjoy good SERPs on very competitive terms.
But, the best use for outward links comes from the law of unintended consequences.
A link sandwich, with two "quality" OGL surrounding one paid link, is going to be next year's top way of not getting penalised for selling text links. :)
It only really helps if the outbound gets an inbound link from the site you just added the link to, i.e., an exchange. :/
I stopped adding outbound links from individual pages long ago just to avoid having to edit/delete dead links. One less thing to think about.
I do have a short list of outbound links on a links page, though. I checked it after a few months and discovered one site started using pop-ups and some black-hat ad scheme. That's the reality of outbound links: you don't know if/when the sites will change.
In terms of SEO I think that it is important what words you use in anchor text and the semantic relevance of these words to the page linked too and from.