Here is a list of ad servers to add to restricted zones in internet explorer.
Adding these to the restricted zones in internet explorer will cut out a lot of ads
on web pages. See list below.

247realmedia.com

adtechus.com

advertising.com

amazonaws.com

atdmt.com

atwola.com

awltovhc.com

clearchannel.com

consumersavingcenter.com

dcreports.com

doubleclick.net

fastclick.net

gawkerassets.com

googlesyndication.com

imwx.com

intellitxt.com

kontera.com

mediaplex.com

pointroll.com

smartadserver.com

snap.com

unicast.com

valueclickmedia.com

youknowbest.com

Thanks, Donald.
Those who use Internet Explorer should find this useful.

Can someone explain how to do that(add to restricted zone)? I recognize several of those on the list as being caught by Spybot frequently. I'm using Windows 7 and IE8.

Start Internet Explorer
Click Tools in the Toolbar
Click Internet Options
Choose the Security tab
Click restricted sites (the red icon)
Click the Sites button
Add the site and click the Add button

Using this method you may have to add the sites separately, one by one.
There may be an easier way where you can copy/paste all the sites at once, but I don't know it.

Thanks, Jenny. When I looked into the Sites button, there were a slew of places already listed there.
Since until this moment I didn't know how to add them, how did these sites get restricted? Do antivirus programs do this automatically?

It could be that an antivirus did it -- or possibly Windows itself if you have parental controls enabled.
I wouldn't worry about anything already being in the restricted zone.

Well, I did have parental controls enabled on the computer when I got it; I've disabled it since there are no children in the house. Maybe that's how the sites got restricted.