I used to obsess about how to transport my bike in my truck, but settled on laying it down and securing the main triangle in two places with tie-down straps.

The good: bike is secure in an idiot-proof kind of way, and is relatively low-profile. No capital outlay for this method.

The bad: bike takes up most of the bed. Doesn't look as elegant as a dedicated rack.

Of the various McGyver options, I like fork mount bolted to the front lip of the bed (under the window, no shell), 'cuz this is pretty secure. Otherwise, the load-lock bar suggested by Moonshot would be a good one, and multi-purpose, too.

Although I would love a high-end rack (Thule, etc.), I just can't justify spending the dough on it.