WordPress is amazing, flexible software, but it doesn’t do everything. Facebook, PayPal, MailChimp, Basecamp, slideshare, and Google Maps are just a few examples of places that are already doing something well, and you can integrate your WordPress site with them through their APIs. However, there are right and wrong ways to do this, especially if you want to distribute your solution to others. I start from the beginning, introducing people to the WordPress HTTP library helper functions, then bring lots of code examples from my plugins show start to finish how to integrate the right way.