A structured journal is a journaling technique in which the writer employs a template or questionaire to help him capture information.
There are some example templates here: http://journal-writing.webdjinni.net/muse-pages/templates/index.html
I've been writing a daily journal for a couple weeks now using modified versions of those templates, and I find that I'm writing more valuable things, and the writing is painless. It is much easier to write when you have something specific to write about, don't you think? Particularly useful are the "weekly summary" and "monthly summary" which ask the journaler to reflect on pleasant or rewarding experiences such as "favorite conversation" and "favorite meal". I suppose I am negative by nature, and by reading my older, unstructured journals, you'd probably have the impression that I never accomplished anything or had any fun. My new structured journal includes a daily catalog of simple pleasures and tiny victories. -- RobertChurch
An example daily template, taken from the site above, follows:
I spent most of my day...Interesting notes on the day...I accomplished...I plan to do tomorrow...I talked to...I learned...Things to remember...Past moments I remembered...I wish...http://www.structuredjournal.com/ is a free template based web application for structured journaling.
See also WonderfulBenefitsOfJournals, WikiJournaling, PersonalWiki