From Meron Fridman’s Blog.
Few montes ago someone asked me about display the content by query webpart as roller (marquee) style. To achieve that goal with the xslt is a problematic solution. So I extended the CQWP with my custom toolpart and override the way it renders. Yesterday I saw that Steven Van de Craen publish his extension to the CQWP as GroupByItemLimitWebPart (extended Content Query Web Part with item limit per group) . So I decided to share my extension for the most useful webpart that shipped with MOSS 2007. I reorganized the code to the same standards as Stevan’s (I like his style…) so you can merge the two webparts more easily.
I attach the solution with the full source code so feel free to change it or to add more functionality.
(You should only to change the “start browser with url” property to your server\host header value in vs project properties –> debug tab. And then right click on the project –> deploy).