The upcoming WordPress 3.2 release will be thankfully dropping IE6 support.  This is a welcome change and means themers and developers no longer have to take a step back 10 years when doing their job.  I believe this change will hasten the removal of the browser since WordPress is a large chunk of the web.  

According to Microsoft's IE6countdown website China has by far the most IE6 installs remaining.  That should mean most sites are relatively safe to get rid of IE6 support (unless your site is in Mandarin I guess).