Not sure what operating system you're using, but Internet Explorer 7 and Firefox both have their own popup blockers. The Google Toolbar is decent and has a popup blocker as well as some other useful tools.

There's almost always a way to get around them though with clever coding techniques used by certain web sites.

if you use mozilla firefox, you can use adblock plus, its worked miracles for me. it doesnt only block pop ups but also unwanted adds.

you can try the google or yahoo toolbar, they both have a pop-up blocker and many other features. You can check this article, for more spyware blocker info: http://www.spywareprotectionunleashed.com...

Linux Ubuntu.

... most popups are aimed at MS Windows ...

Here is one among many:
StopZilla!

http://www.stopzilla.com/products/stopzilla/home.do

Most Advanced Pop-up Blocker Available

* Blocks Pop-ups spawned by Spyware, Adware, websites, and other sources.
* Detects, blocks, and quarantines Spyware and Adware in true real time.
* On-demand & automatic Spyware scanning.
* Updates automatically for optimal protection.
* Kills Browser Hijackers, removes rootkits, prevents botnet attacks.
* Blocks Phishing Attacks, protects from malicious Web sites.
* Clears Cookies & History.
* FREE unlimited customer support via live chat, e-mail or toll-free calls.

Use Firefox browser. The built-in popup blocker is very good. Blocks almost 95% of the popups.