Google dropped IE6 support for YouTube over a year ago. They are dropping Google Apps support for IE7 on Aug 1st (that's today for some people reading this).
For search results it's probably more worthwhile and not as hard to support the IE's but for their other apps they say they are only supporting that two most recent browsers.
Google Search dropped mainstream support for IE6 last fall. IE6 users are served a degraded experience that is roughly on-par feature-wise with Google Search as it existed in May 2010, and new features are no longer rolled out to IE6.
And this is how IE6 will slowly be deprecated across the industry. Sure it's easy for an intern to get up on his soapbox and proclaim, "We should stop supporting IE6 because that browser came out while I was still in elementary school." But when you look at the how many people still continue to use it, deprecating support is on a case-by-case basis, and it is irresponsible as web developers to just ignore that it even exists.
I would actually argue that Google Search is still supporting IE6, just as a degraded experience. Dropping support all-together means they just ignore it exists, which is far from the truth and likely won't happen for 5+ years.
Well, under that standard, Google Search still supports Netscape 4.7, which is also served a (slightly different from IE6) degraded experience. I wouldn't be terribly surprised if it supports Netscape 1.0 and Lynx either.
For search results it's probably more worthwhile and not as hard to support the IE's but for their other apps they say they are only supporting that two most recent browsers.