I just posted a new article containing a list of available online security resources from Microsoft. It's not the end-all, be-all list of security URLs, but it does contain a large number of resources, some of which you may already be familiar with, and some that you may not have heard of. Please take a look...since this'll be up there for a while, please do let me know if you discover any broken links, and I'll get them updated ASAP.

http://blogs.msdn.com/gduthie/articles/240865.aspx