This Old House - MOST REQUESTED: If you decide to DIY install your ceiling fan, here are a few things to know - Get a fan fixture box: This type of junction
Installing Ceiling Fans
How to Install a Ceiling Fan (DIY) | Family Handyman
RACO 1-Gang Metal Old Work Ceiling Fan Electrical Box in the Electrical Boxes department at Lowes.com
How to Install a Ceiling Fan Electrical Box
HOW TO PUT IN A FAN SUPPORT OUTLET BOX - YouTube
How do I remove an old ceiling junction box to install one rated for a fan? - Home Improvement Stack Exchange
ceiling fan wobbly, electrical box is loose - DoItYourself.com Community Forums