A few personal favorites:
Security for Everyone: http://securityawareness.blogspot.com/
Windows Security: http://sunbeltblog.blogspot.com/
Practical Corporate/Enterprise Security / Security News : http://taosecurity.blogspot.com/
btw – do you know that Internet Explorer has 25 security holes, that’s yet to be patched by Microsoft ?
It doesn’t affect me though since I’ve been using Opera/Firefox for quite a while now.