There are two main classifications of sites that everyone who wants to own a web business should know about. Hub sites and Authority sites.
Authority sites are sites that are considered an authority on a specific topic. For instance, I think it is pretty safe to say that CNN® is an authority site for news.
The details of what makes a site an authority status is up for debate. Generally speaking a website that has links from many sites with the same theme, that has lot’s of information on a particular theme, and that ranks highly for related searches for that theme, are likely to make it an authority site for that theme.
Hub sites on the other hand are web sites that contain a lot of links to sites that have a particular theme. Many of the top directories are considered hub sites. To become a hub site for a particular topic your website needs to have links to a lot of websites related to that topic, and especially to highly ranked websites for that topic.
A website can be both a hub site and an authority site, which is really the best of both worlds. Both hub sites and authority sites rank high for related search terms. Most blogs have a good chance of becoming a hub site for a particular topic, because those who blog tend to link out to related sites. Blogs also have a good chance of becoming authority sites, because of the amount of content related on specific topics that they build up over time. This is one of the reasons that blogs tend to rank so high in the Search Engines.