"Using Regionally Oriented Materials in a Writing Center" (on dialect); "A Five-Minute Diagnostic for Writing Labs" (predicting student performance via error-finding exercise); reports from labs; "Handbook for Tutors" (description of an in-house training manual)
Baruch College's Writing Center has curated collections of handouts on various topics (writing process, analysis and argument, structure and organization, grammar, etc.). A large collection of handouts drawn from many colleges and universities.