All these modules are related to blogging, and information gathering, rather than social networking, or any of the other roles Drupal fulfills.
Related Links
The related links module allow you to specify external links which relate to the entry. It also, automatically extracts links from the body. These links can be displayed in a Related Links block, as well as those related by topic in the Related Topics block.
The use of a multiline textarea to store the extra links, in HTML markup is a bit of a drawback. This has a couple of issues. One, if you have a Rich Text area installed it will stuff things up for you. And secondly, requiring the links to be in HTML is a bit of a drag for userfriendlyness.
Another useful feature would be to allow authorized users to add extra links through a button on the block. So, as relivant links arrise they can be easily added.
Similar Entries
This is a content level related link. This appears to be a really cool and interesting way to get related content. However, when I tried the module on my test site the block never displayed.
Panels
Panels offers a neat structured layout based on blocks and HTML elements. This allows you to transform the front page from a blog link news site, to a professional, non-scrolling introduction. This seems to be a very neatly put together module, including AJAX lookups for nodes.
Hopefully more to come soon.