Maybe it's new -- maybe not, but another Google query refinement test is out in the wild, as covered in our SEW Forums thread Google Refinement Keywords. There are links to screenshots showing that after a search, a "Quick results" area appears at the top of the page with links that seem to narrow refine results into clusters/topics. Something similar was seen last month.
The topics and implementation resemble what happens after a search at Google Base , such as with apple, which brings up this at the top of the page:
It makes me wonder if the refinement is going along with some Google Base material flowing into the main web index as part of a test.