I'm amazed I only found one relevant suggestion. Jon Skeet suggests a user interface for searching for a link on a selected 'API website'.
I'd go one step further and use a mechanism as e.g. Wordpress has when editing a post.
In the screenshot above, because the content of the post contains 'lap dogs', underneath a recommended link to the wiki article on lap dogs shows up, along with 'Shih-tzu' and 'puppies'.
Basically an automatic google search is done for you for the content of your post, and link suggestions are highlighted. Combining this with Jon Skeet's suggestion, the search could be made smart enough to only search relevant resources. (API websites etc ...)
A database of 'relevant links' or entire domain names per SE site could be added and managed by moderators.
Example for Stack Overflow:
Links from the msdn domain name would be considered as valid suggestions, but also wiki pages for software design patterns. When writing MVC pattern in your post, a link suggestion to the wikipedia article could pop up, so all you have to do is click on it to link to it.
The 'related' SE links could also be used.
A couple of possible advantages:
- When instead of linking to an url, you link to a link stored at Stack Exchange, you can update the link across the entire site to a new source when the original link gets outdated.
- More links will be added to relevant posts, resulting in higher quality posts where additional data can easily be found without having to google for it yourself.