Crash n Burn

Well... a lot has changed in 3 months. Formerly stable sites have disappeared into the void, nothing more than another statistic in the GPT world. PTRs that have been actively paying for over 1 year are few and far in between. If you're looking to make money from just PTRs, forget about it. It's a saturated market, where the average PTR disappears within 3-6 months. No... the real money is to be made in contextual advertising. What's that? Basically, these are text ads that appear on websites that offer related products to your site visitors. For instance, your site could be about the different places you've travelled to, and the ads could be from travel agencies, airlines, etc.
Google Adsense is the most famous of the lot, making heaps of cash for those who know how to use it properly.

Of course, if you're promoting GPT, contextual advertising is not an option. Paid-to-Click does not comply with these sort of ads, as advertisers pay for valid (genuine) traffic. GPT will forever be a mistrusted 'business', due to the high % of fraud that can and may occur with it.