We don't have a system for issuing certificates for course completions, but we do have a Code School Report Card page that you can use to show off all your course progress. We did have course completion sharing via LinkedIn, but this is no longer supported at this time. You can share via Twitter and Facebook though!
Every user has a Report Card page for their account. You can access your Report Card by clicking the link on your account dashboard.
Here's an example of what a Code School Report Card looks like. And this is set up so that you can print to PDF, which would be something similar to a certificate.