I really like this article, Biggest Bang For Your Buck In Time Trial Equipment, it discusses "drag difference" of different equipment for a bike and the cost of that equipment. I am thinking I need to get an aero helmet some time soon! :-)
Bicycle Repair Guide - Video Tutorials, lots of "How To" information for your bike. I have to admit I haven't read a lot of information on here but I do want to when I have more time.
When I finally bought myself some aerobars for my bike this video, Maximizing the Aero Position, was really helpful for installing them and body positioning.
And the last article, Triathlon Fit on a Road Bike, discusses some adjustments that need to be made and what to look out for when adding clip-on aerobars to a road bike.