Personal observation: if you're forced to use popups or popunders to get a response from your visitors -- maybe you need to rethink your page layout and marketing focus.

What do you really want them to do when they hit a web page? Don't have that page offer six or eight different options (so that you want them to buy a book, join your marketing circle, sign up for your newsletter, and agree to receive mail about joint ventures ALL on the same page.)

Sectionalize your website/web pages. Have each page focused on something different (think of CNN.COM... links to stories on the front page, and each story is within a section (entertainment, world news, us news, sports, financial, etc.) The marketing in each section "harmonizes" with the stories (no offers for Sports Illustrated in the financial section).

They don't just dump everthing on one page.