I do receive a lot of emails from people who are seeking for help,specially since my blog's anonymous comment has stopped working and I lost all my comments :(
I usually keep all the questions in an Excel sheet for further analysis. The other day I had the chance to go over all the questions and to my surprise; one of the most frequent questions is about content query web part and in particular this question:
“Why Content Query Web Part is not showing up in my web part catalog?”
There are two important things that you need to remember.
First of all, CQWP is part of MOSS 2007 and not WSS. There is a workaround (with some drawbacks) to implement CQWP functionality to an extend in WSS .Check this out:
http://www.u2u.info/Blogs/Kevin/Lists/Posts/Post.aspx?ID=8
Secondly, Content Query Web Part along with Summary Link Web Part and Table of Contents Web Part only show up if you have the Publishing Feature enabled on your site collection.
Hope this helps.