Rpgresearch

By far the single best free and open site to start at when performing role-playing game research studies on the effects of RPGs. There is no paywall, nothing to buy, and no annoying ads. They are a 501(c)3 non-profit research and human services organization studying the effects of all role-playing game formats: tabletop, live-action, electronic, and hybrids. They have more than 10,000 (ten thousand) items useful for research, such as essays, papers, panels, audio, video, graphs, data sets, original and archives research studies, and more. Best of all it is all free! They are completely volunteer run, been online since 2004, and the founders involved with role-playing games since 1977.
The site could use some better organization, but it is well worth getting to know where the nooks and crannys are. They have thousands of content items you can't find anywhere else, not even in University libraries or databases.
The biggest challenge is that because they are volunteer run and donation dependent, sometimes the research archives aren't completely available at every hour of the day. They are getting better and better each year as they improve their hosting and design options.
Also they have announced they are opening a facility in Spokane, Washington as an RPG Community Center and role-playing game museum. I haven't seen it yet, but when they announce the opening, I hope I can check it out.