LMU's SoTL Discussion Group meets monthly. Everybody is welcomed to attend, even if you are only curious about what other people are doing. (Contact Curt Bennett or Jackie Dewar for meeting times.)
One of the key researchers scientific reasoning is Anton Lawson.He has posted many of his recent papers related to cognitive development and learning science.
A rather large, annotated bibliography of SoTL work.
Like all research fields, doing a search of the literature is an important first step. The following a couple of lists which show the SoTL publications for many disciplines. (These are also good lists to check out when you are considering where to publish your work.)
Illinois State also has a fantastic list of resources sorted by discipline. This list includes web sites, journals, and professional societies that support SoTL.
The Carnegie Academy for the Scholarship of Teaching and Learning (CASTL) is a great organization that has been to the advancement of SoTL.
One of the innovators in PER is "Joe" Redish. He has many of his papers and projects post to of his group's web site. A few articles that merit special attention:
Several other research groups are also looking at epistemology and metacognition in physics: Colorado, Rutgers.