People using Internet Explorer on computers running Windows should severely curtail their web browsing in the next few days.
Reports indicate that there is a complex attack in progress on the Internet in general where websites are being compromised in such a way that visitors to those websites that are running IE on Windows may be infected with malicious software.
I'm usually the guy that tells people to relax when the media puts out a "gloom and doom" warning, but I'm taking this one seriously.
UPDATE: Microsoft has some marginally helpful advice here.
Steps You Can Take: Don't surf the web at all.
If abstinence is your answer, make sure you follow through. The reports indicate that some well-known web sites are affected, so until more information comes in, don't assume that any site is safe.