Aside from APA and what has been mentioned, I don't think many therapists use commercial/privately-owned type websites, blogs etc. for reference. Sometimes forums for discussion/opinions. Often various "official" research databases online or through universities; usually need access. Also local licensing boards and/or managed care orgs often have "provider resource" type websites where you can get handouts, training powerpoints, tests, etc. So looking at a few state boards you might find links.