prevx
By time in time i read prevx blog: my dear friend Marco, known as eraser, work for them and write on their blog.
It's fully of interesting articles about virus internals, how rootking works, how malwares evolve and so on, but this time they beat them self: The Ultimate Prevx Blog Linkage Extravaganza!
Look at this post, it's amazing!
http://www.prevx.com/blog.asp?ID=18