Everyone appears to have a speed test of their own nowadays.
Netflix launched fast.com more than a month ago; SourceForge released their new HTML5 speed test soon after.
Google appears to want a piece of the action as they are trying out a way for people to check their internet speed by simply typing "check internet speed" into search.
The tests are performed by Google's Measurement Lab tools, and were first spotted by Pete Meyers, who posted a screenshot of the feature and discovered a Google Support webpage detailing how it works.
The feature has not been widely released yet, but it's possible we'll see it made more widely available soon.