I have less than 3% IE users on my website (targeting webdesigners / developers). So I don’t support IE9-. No point.
It really depends on your target audience, but in most case, you can drop support for IE6, and IE7. IE8 is still the latest version of IE on Windows XP, so you may or may not consider supporting it depending on your goals.
Where I work our policy has been the latest browser and then one back. So currently IE9 and 8 but they are planning on moving to IE10 when it comes out, though that will probably be a slower transition than I’d like.