In December 2012, Google launched a data highlighter tool that aided more novice webmasters in creating structure data for use in the rich snippets in Google's search results.
Google announced that they added more data types support to that tool, which we covered two weeks ago. But they also added a web based version of that tool, that instead works within the browser and produces the HTML for the markup for you.
The tool is named the structured data markup helper and it basically allows you to select your markup type, highlight what you want to markup on your page and then outputs the HTML for you to copy into your code.
Here are screen shots of the tool in action:
The addition here is that it also produces gmail markup for richer emails.
Forum discussion at WebmasterWorld.