Going to add to the guide a little bit based on other questions I've received.
-------------------------------------------------------------
Q: How do you link out to sites?
A: The following advice only applies to your money site. There are completely different suggestions I have for your web2.0s, as well as your blog network. Only apply the following advice to your money site.
1) Only link out to sites that Google currently considers better than your own. Only link to authority sites, preferably .edu or .gov sites, or another highly trusted site.
2) If you're going to link out, have it be a do-follow. When you label something nofollow, you're essentially saying "Hey, Google -- I'm a professional SEO! And I DO NOT vouch for the site I just linked to (it could be complete crap, I don't know) so don't trust the link I just made to them!" If you're going to link out, take credit for it. Also, you're not saving your PR by nofollowing, you lose PR when you have an outbound nofollow link.
3) When you link out, you're losing something and you're gaining something. You're losing PR. You're gaining a relevancy signal, telling Google that you are a decent resource for the subject matter to which you just linked. If it is an extremely relevant link, that helps your entire website (this is one of the 200+ factors that Google is juggling when it evaluates where you should rank). Don't consider it a net gain though, you're losing PR and you're gaining in this relevancy stat -- its a wash-out. Therefore, only link where it makes sense to, you're not losing anything by doing so.
4) As a rule, only link out to a website once, sitewide. If you're going to cite wikipedia on the 5th post of your blog, don't cite them again on the 10th post. Find new resources. There may be a diminishing benefit to linking out to the same site repeatedly.
5) Don't go hunting for reasons to link out. If its a natural thing to do, because another website is a useful resource that should be mentioned in the context of your article -- do it. But don't say to yourself "I need to cite something in this article to make it valuable", don't go looking for reasons to link out.
6) Limit this activity sitewide. PR is something you want to keep on your blog, and if every page of your website has outgoing links -- that's an aweful lot of PR you're allowing to escape that you could have otherwise recirculated through other pages of your blog. Personally, I wouldn't link out any more than once every 5 blog posts.
How does this differ from your web2.0s and blog network?
Upon creation, your web2.0s have NO PR. In-and-of-themselves, they haven't got a bunch to offer (they help by increasing the Class-A IP addresses that link to your site, as well as a little juice from the articles you create). Their purpose is to 100% be a resource portal, this happens when they link to your money site as a resource. Linking to only 1 site, however, doesn't make a web2.0 a resource guide. Web2.0s are going to milk all the "authority juice" they can by linking out to other high quality resources. Every page of your web2.0 should become a mini resource directory for a keyword. It links to all these high quality resources, and it also links to your money site. That gives Google a signal that your money site is a high quality destination for that particular keyword. Every article I make on a web2.0 has approximately 3 to 4 outgoing links, 1 to my money site and 2 to 3 going to high quality .edu or .gov sites that rank well for my keyword. Never link to the same resource twice (other than your own) ... after you've linked to one college site, pick another one the next time. This is to increase the different sites your web2.0 links to (again, this linking out generates some type of credibility with Google for which the web2.0 gets credit, meanwhile its not wasting any PR because it has none to start with).
Your blog network, on the other hand -- wields tons of PR. You don't want to drip it all away by linking out to unrelated resource sites. Every little drop of PR on your high PR blog network should be reserved for converting it into a highly relevant article pertaining to a keyword you're chasing after, and then linking to your money site from that highly relevant article, passing every last drop of PR it can. When you do this, you're also passing along authority the site has (assuming your blog network has high page authority and domain authority).
Now I just stated everything above as canon. In reality, maybe 30% of what I quoted above comes from what I've heard Matt Cutts say, 50% trying to second-guess Google and the way they would look at things algorithmically, and 20% refined from personal testing.
Nothing what I stated above will hurt. Most of what I stated above I'm using educated guesstimates based on what I believe Google would do from an algorithmic point of view. Most of it I don't know for certain, and neither does anyone else. But I have success with the above methods, so if you want to skip the guessing and just do something that works -- the above will work.-