Thanks. It's fairly simple. I do it all in Adobe Camera Raw (part of Photoshop CS3), all global adjustments without any need to open Photoshop itself, other than for resizing and sharpening (although if you're so inclined the look could certainly be refined in Photoshop). It would be very similar in Lightroom and I imagine you can do the same kind of adjustments in most raw processors.
The light has to be right in the first place - whether natural or not. For these biker shots it was bright, directional, late afternoon sunlight.
In ACR...
Adopt attitude of reckless abandon
Rein in highlights with recovery
Lift shadows (quite a lot) with fill light
Push black point until it feels right
Boost contrast & clarity...tweak tone curve...adjust exposure & brightness if necessary
Boost vibrance, while cutting saturation
...carry on tweaking until desired look is achieved
You need to get a feel for how adjusting one setting affects other things - eg. if you use much fill light, you will almost certainly need to boost the contrast...the more you push the black point, the less vibrance/saturation you need.
Actual settings will vary considerably from image to image.
Hope that helps.
Here's one I took today, although I know nearly nothing about how to take pictures I just basically point and shoot 
