This is a fantastic comment system that can be very easily integrated into popular blogging platforms, and I believe a few CMSs. In addition it integrates global avatars (gravatars: http://en.gravatar.com/) upload avatar and many more fab functionality.
"fund raising standards board" FRSB tick credibility logo competitor, but free with no fee ;o). A service to put the minds at ease of potential donors. How good? Dunno, got here from Thirdsector Mag.