Ten Things About Outlining Your Fiction
I haven't yet tested Using MS Word to Auto-Outline and Keep Track of Revelations by Martina Boone, but it sounds like it should work.
Keith Cronin abstains from Roman numerals in his hybrid pantser-plotter approach to outlining, The Big O.
Glen Ford's Book Proposals ~ Writing an Outline for a Nonfiction Book from the Book Itself and How to Reverse-Outline Your First Draft by Mark Nichol both tell you how to write up an outline after you've written the book.
If you want to know how Janet Evanovich outlines (aka the easy way), take a look at her storyboard method and how she plotted one of her novels here.
Janice Hardy discusses putting together your own outlining method in Are You In or Out? Crafting Outlines That Work for You.
The Outlining Dilemma - Plotting vs. Pantsing by Beth Hill discusses the pros and cons with both approaches, and has some useful tips on outlining that work for both.
Sarah A. Hoyt's Hunting the Wild Subplot is more about the process of refining an outline than subplots per se, but still worth the read.
Alicia Tasley's classic article Outline Your Novel in Thirty Minutes asks all the right questions; you provide the answers.
DIY MFA's Untraditional Outline Techniques article includes a link to a one-page worksheet to help with outlining the primary elements of your story.
Juliette Wade's Sequence Outlining offers an event-driven method of outlining.
All of the above links were found via the fabulous writing-specific search engine at Writer's Knowledge Base. And if you'd like to see what I've written on outlining here at PBW, click here.