PPC still doesn’t have a direct USD trading market. Crypto-Trade now support USD trading for LTC, NMC, XPM, FTC. I would like to see PPC/USD trading pair supported there too.
Let them know that you are interested in this trading pair as well. You can ask them about it in the chatbox on Crypto-Trade or pm Crypto-Trade on bitcointalk.
Update: crypto-trade began support of PPC/USD trading (Sep 9th).
Trading volume of PPC has significantly increased recently on crypto-trade. Let’s thank neotrix and crypto-trade team for their excellent support of PPC and XPM trading