Robert Martin is a guy our CEO and architects really respect when it comes to software design and development.  Somehow, I managed to not have heard of the guy before this year, so I’ve started reading his stuff.  Here are a couple of his older columns that may prove quite useful if you find yourself building APIs in your work:

The first one explains a lot of the issues I've seen with applications in previous jobs.  In any number of applications, a simple change would have a ripple effect that touched a lot more than just one line of code.  Following the open-closed principle more strictly would haved save me many headaches.