You can try tradingcarddb.com (Trading Card Database). An excellent site for tracking your collection as well as a very friendly and helpful forum community. Many people over there trade or are looking to trade.
My other trading site, the first one I found back around 2007 when I discovered the online community, is Trading Card Central (TCC) tradingcardcentral.com is also a nice place but I think the traffic there is even slower there. There are some regular members who continue to post, but it isn't as active as it once was a few years ago.
It seems to me that there is an internet wide lull in activity on trading card sites. I think some of the traffic has migrated to social media. It seems more and more people are doing all there trading via Twitter and Facebook. I understand they are great places to do that but I am not of the crowd that will be doing trading on social media. I guess I'm just old school (in more ways than one). Like wanting my television programming via my television not computer or internet, I prefer my trading card trading via trading card forum sites and blogs not regular social media. I don't want to bore my family and friends on Facebook with my hobby details and I very rarely use twitter anyway.