Social netoworking features such as blogs, forums, and event calendars as well as more elaborate features, such as e-commerce are usually implemented at this point.
If your site involves these types of features, it usually makes the most sense to build the "core" site first, allowing you to get started publishing your main content, and allow me to continue to work in parallel. That way, you can do a "soft launch" of the site and make it public before the full version is finished. These more-coding intensive custom features are then finished after your site is live.
In general, these features follow a similar sequence as above. In most cases, we do most of the visual and functional design of the advanced features in the design phase but defered until this point. For example, if your site has an e-store, we design some templates for it at the same time as the core site, so it has a unified look and is intelligently integrated into your site. However, we then start the actually implementation after the "core" site is done, so that you can have a web pressence (or just a new look and new content) before we begin the e-store.