National Wood Flooring Association
The NWFA provides valuable information on wood flooring and finishing. The site is geared towards the hardwood professional in mind but can be very useful for homeowners as well. Check out their Find A Certified Professional tool!
Clarke American Sanders How To Video on YouTube
This is a link to the first in a series of How to Sand Wood Floors videos produced by a leading floor sanding machine manufacturer. The video series available on YouTube contains many useful tips.