A new page on the TMS Wiki details various approaches to journaling. They’re up there to help people with chronic pain, but journaling can be a big help to just about anyone. Among the approaches on the page: List Making, Spider Writing, Free Writing, Unsent Letters, and Dialogue.
Several workbooks, which’ll help you through the writing process are listed. Two chronic pain-specific, journaling-heavy titles: Unlearn Your Pain (Dr. Howard Schubiner) and The MindBody Workbook (Dr. David Schechter).