Google has been allowing AdSense publishers to block category of ads since April 2009. Later on that year, they expanded more categories. Then a month ago, Google expanded this program a bit more to allow "general category blocking."
This beta program will allow some AdSense publishers to block 170 more specific categories, including finance, travel, job, and automotive. This feature will allow publishers to block up to 50 ad categories from among a broad range of 170 fine grained categories.
Yesterday, Google began inviting more publishers into the test group.
Here is a picture of the console:
Forum discussion at WebmasterWorld.