I use this heavily in my projects to fix IE's inferiority. Here's what I do.
<!--[if IE6]>
<style type="text/css">
@import url("/css/ie6.css");
</style>
<![endif]-->
<!--[if IE7]>
<style type="text/css">
@import url("/css/ie7.css");
</style>
<![endif]-->
By using the @import you can keep all your hacks in separate css files and just include them into your page. Make sure the code snippet is in your <head> </head> tags