I don't know how nice you want it, but when I bought my truck I built a rack out of 2x4s. Couple slots for the for the front tires to go in, then bungee cords to keep the bike vertical, and the rear tires from moving around.
What level of security are you looking for? I won't leave my bikes unattended for very long, but if I'm on my way home and want to stop at the grocery store, I have a 6' cable lock I use to attach the bike to the truck (the kind you use to secure tools in the back of your truck).