github-renderer is a utility that lets you view rendered HTML pages from github repositories on the fly.
Alternatively, if github allows you, you can drag [this] to your bookmarks bar.
These are HTML pages from various repos.
Browse them and click on the "github-renderer" bookmark to render them.
Note: make sure you allow pop-ups from *.github.com in your browser.
Note 2: This works best with Chrome or Safari. Firefox won't load js and css files for some of these links.