My IT Forums is perhaps the best free resource for supporting Microsoft technologies.  While it started as an SMS support center, it has expanded to cover a number of important topical areas.  We had some good sharing on corporate spyware and adware protection as noted in the links below:

My IT Forums - Corporate Spyware/Adware discussions
http://myitforum.techtarget.com/forums/tm.asp?m=62741

One of our members did an excellent job of summarizing all the posts.  The May 26th blog entry provides an informative status of adware/spyware protection in the corporate environment: 

Roger's Information Security Blog (May 26)
http://www.infosecblog.org/