If you are an IT professional or heavily into Windows security, then check out and subscribe to the Microsoft Security Notifications. This site offers a variety of ways to be notified including an email subscription or RSS feed.

Additionally, you can search for recently released notifications as well as choose the level detail covered in the description (simple or comprehensive). If you do subscribe to the newsletter, you do not get spammed (I can attest as I am a subscriber) and the information is quite relevant.

Again, worth a look if you are into security at all.