Links, the cornerstone of off-page SEO elements are widely considered to be external references pointing to the pages of a website. Link Building is usually considered to be an activity which has nothing to do with the website. However, delving a little deeper in to the link evaluation strategies of search engines will make you realise that links need not always be external and that a lot of value can be derived by making good use of pages within the website itself. In fact, an understanding of Google PageRank can help you identify that links to a page for quantification purpose, are counted merely in numbers and one of the best ways to acquire these numbers are pages that are a part of the website themselves. So, how to smartly use these abundant links (through pages within) and derive maximum link equity?
Here are a few suggestions -

Hierarchical Organization

Arrange the website as an organized hierarchy of pages. This will automatically yield the sitemap structure. For large websites, the hierarchy can be separated into sections and sectional sitemaps can be generated, controlling the amount of links on the sitemap pages. The hierarchy also helps in generating XML sitemaps, used largely by the search engines.

Intra sectional linking

With the website being organised hierarchically, sections (or categories) are natural fallout. These sections are basically closely related collections of pages and provide an excellent opportunity to create a closely linked structure within them. Intra sectional linking can be achieved through sectional navigation (e.g. section oriented left navigation), section focused footer linking etc. As links to every other page within the section exists on all pages, it results in close coupling of the sectional pages leading to a strong intra sectional linking scenario.

Inter sectional linking

Inter sectional linking results from cross-references as well as categorization within the hierarchy. Typically, inter sectional linking happens between pages separated by a level, such as categories and sub-categories, where all category pages link to their respective sub-categories and all sub-category pages link to their parent categories as well as other categories at the same level as their parent category. Effective use of this technique helps to generate inter sectional link mesh.

Follow through navigation

Due to inter relation between content and pages, a user can take multiple routes to reach the same page. A clear listing of all these routes originating from the home page provides follow through or "breadcrumb navigation" as it is popularly known. The technique is especially effective for eCommerce/content rich websites, involving multiple levels.

Content based references

Links from within the content are perceived to be the strongest of all link forms. Hence references, from within the content provide excellent opportunity to target adhoc, yet extremely valuable content references. As these links cannot be planned for, they also have the advantage of appearing extremely natural form of links.

Glossary/Dictionary

For large websites, it makes sense to create a glossary/dictionary of terms (especially domain related keywords) and provide automatic linking to appropriate pages describing these keywords/terms in detail by means of dedicated pages, which are specially promoted for these keywords.

Custom Errors

As a website grows, some of the linkages become redundant and if the site is cleansed of old content, there is a high possibility of broken links getting created. In addition to that, changes happening every now and then result in navigational errors being created and that should be handled by creation of custom error pages, which helps visitors and search engine spiders maintain context within the website and helps strengthen the link mesh.

Inter related information

The concept is particularly applicable to news or blog sites, where new content gets added frequently and strong content relevance can be generated by clubbing together related content and information. For e.g. blog posts/news items which discussed belonged to the same topic/news thread.

Now, it's obvious that not all of these techniques are relevant in every instance. However, making use of all the applicable strategies will enhance the link strength of your domain, helping it derive maximum link equity through smart use of internal links, which are by default available for free! For any other link building requirement though, you can always utilize link building services from an expert company.