sFLOW collector?

I am trying to implement sflow in my network, and looking for a free sflow collector, that I can use to better see my peer to peer, and route utilization. Right now I have the problem of not knowing how much of my traffic is coming/going to what ASs. I have installed ntop so far, but don't see the tools/benefits that I am looking for to help me specifically with the BGP. Is there a plug-in that I am missing or something. If someone could point me in the right direction, or recommend another free collector that could help me out, I would greatly appreciate it. TIA, Darrell