Firefox and Chrome have Adblock.
Does anything similar exist for IE8?
By similar I mean:
Easy to install
Trusted (that is, reviewed by somebody credible)
Rather than installing software or some add on, here is a non invasive way to block anything you want on any browser in Windows
K9 Web Protection is a child's (or children's) web filtering and blocking software that is extremely configurable. You could turn off all the settings that you didn't want (filtering, word block, site block, category block, time limits/restrictions), and just use advertisement block feature. It works cross-browsers; one configuration covers Internet Explorer, Firefox, and others all one the same machine.
K9 Web Protection: http://www1.k9webprotection.com/
Did I mention that it is FREE? Highly recommend and does the job well.
For Windows only, and works very well. Installs separately - not as an addon, and all configurations are protected by a password...