I realize it's close to April Fools' Day, but this is not a joke: you can actually use Firebug in IE. Well, sort of. Joe Hewitt, the author of every developer's favorite Firefox extension, has created a Javascript file that you can drop into your web pages and, voila, you get the debug console. And it works in IE. I realize this isn't quite as good as the full blown Firebug, but it's sure a lot better than the alternative:

<script>// <![CDATA[ alert('this sucks'); // ]]></script>