We use two "Insta-Gator" brand bike racks to carry our two mountain bikes in the bed of Justin's F-150 pickup. Two bikes will fit perfectly in most full-size pickup truck beds, but since our pickup is a 4-door ("Supercrew") model, the bed length is about 1-1.5 inches shorter than the bikes are long. We almost returned the InstaGators until we learned the ONE way the bikes will fit securely in the Instagators in his truck bed -- the bikes have to go in at a slight angle, each with its rear tire in the corner of the bed, and even then the handlebar ends touch. But, it's a secure fit and one that eliminates having to carry them on a tow-hitch mounted rack which seemed a little less secure to us (from a theft standpoint) and a bit of a hassle from a parking perspective.
If you're handy, I've seen people with home-grown (wood bolted to the truck bed with a notch or other way to 'capture' the tire) truck bed racks that'll be far cheaper than any store-bought rack. The InstaGator's are nice because they're held in place simply by the tailgate being closed and they quite securely grab the bikes' front tires.
About in-bed truck racks/mounts -- If you have back problems or you're short and have a 4x4, a bed rack might be a hassle though. I usually let Justin heft our bikes into his truck bed because with my height (or lack thereof) it's a struggle to get a bike up into his truck bed all by myself. My sedan's bumper/trunk rack is far easier to reach!
I can't remember the brand of my rack -- will add that to this post tomorrow. They make a 2 bike and 3 bike model; we have the 2 bike model for my sedan since we only have 2 bikes.