There are probably tens of thousands of skills in the LinkedIn skill set, and there is no API to download this. You can go to http://www.linkedin.com/skills/ and type in some skills that are relevant to the website or volunteering organization and you will get lists of related skills - you can probably pull together a pretty comprehensive list by following the chains of skills.
LinkedIn announced that they shut down the GitHub application, as of 26 November 2012. Now, LinkedIn only offers this, for sharing from Github:
You still have the option to share your code from GitHub on LinkedIn
by sharing links on your homepage or in groups.
In other words, you can share links from Github the same way that you share links from anywhere else online. That is just the same old, manual feature as in the past.
Best Answer
LinkedIn's Top 100 Certification Providers (based on the number of certifications in profiles).