For those of you who are looking for more and more traffic sources to run some traffic on, here are all the ones that I know of that offer pay-per-click (PPC) models. For those not 100% sure how PPC Works, please read an earlier post on it.
Google Adwords – The strongest of all PPC sources still can make you tons of money if done right.
Facebook - Tons of traffic, though approval takes awhile and is highly restricted with what they allow.
MSN Adcenter – Strong traffic, though nowhere near the first two
Plenty of Fish Ads (POF) – Awesome ad inventory from this dating website giant
Feel free to let me know about some more in the comments area and I will add them to this list. Hope this helps you find some new sources to try out!