YAMLlint - The YAML Validator
Jay Jamison stashed this in Codilicious
Had an internationalization bug in a little code project, owing to using tab versus spaces for the en.yml file. (Who knew?) Found this site, which gives a quick verification that whatever yml you're writing works. Stashing to make hopefully easier for future n00bs like me to find in the future.
Tab versus spaces bugs are surprisingly common even now.
Good verification tools are a good line of defense.