Pop ups and pop unders are annoying. Most "free traffic" does come from sites with iframes that load your site in a 1x1 pixel. It is a waste of money!
I think the best way to get traffic to your site is to get involved with social media sites and master them to improve your traffic over the years.
Wanna check SEOClerks? You will get great results thats guaranteed http://www.seoclerks.com/categories/Traffic
The best place I have found to get REAL traffic from is a site called; www.projectwonderful.com It is an amazing, useful place to place banner ads on real sites for cheap prices. Like, seriously cheap prices. At a glance, you can choose from thousands of sites in just about any niche you can think of, you can see how much traffic the site has received over the last 30 days, you can see what sort of bids people are making to advertise on the sites and you can geo-target sites for US, Canada, Europe or elsewhere. I personally have sent heaps of traffic to my books on Amazon Kindle using this site. It really is a hidden gem. In my humble opinion.
Should have mentioned, even better, the traffic BUYS! I am not an affiliate of project wonderful. I just love making money with it.