Google Labs added four new offerings to their already rich set of optional features you can enable in Google Mail. The new features arrive in the form of previews for different site content, specifically YouTube, Flickr, Picasa and Yelp. The new Labs features all work the way you would expect them to, activating when a link to one of these services is detected and appending the message with a small gallery.
Of course, each of these services offers a way of sending a content-enhanced email to your friends without much more than basic HTML support on the other end. But often, it's easier for people in a hurry to just drop a URL into an email and fire it off. That's where these features help - they often save you the step of having to navigate over to the linked item.
We do like the idea of these features. But in a way, these features are walking a line that Gmail has carefully been avoiding in directly marking up the information inside an email. Of course, we realize these features are optional and that Google already mines email contained within Gmail for keywords to power their contextually-sensitive ads, but these tools go a step further and modify the content of the message.
We would also like to note that the enhanced content is not in the printable view, so if you were thinking you could quickly print out that email with the attached Yelp review, you will find the additional content isn't there. That said, these features are fun and are another stepping stone for Labs in their continuing quest to find ways of constructively enhancing the Gmail experience.