Very well executed -- relies on peer reviewed sources and provides links to journal articles when available. For several topics, provides varying depth of explanation -- for both the novice or those interested in acquiring a high level of expertise. Hard to do better than this online.
What many fail to understand is that science is debated by those doing the actual work in refereed arenas -- the scientific journals. A lot of the stuff available online is amateur, politically oriented junk. If you really want to seriously begin digging into this topic, and want to bypass all the junk science out there, this is a great place to start!
Kevin#93 about Skeptical Science, v1.1.0