I've heard of Pilot Air being pretty cheap if it warrants a flight I guess. uShip might be cheap too but then again it's just "people" handling your stuff. Just hope you don't get a jerk I guess. My dad did business on that site for a while and he's really really considerate at what he does, but I would imagine some others are not. (Or are just bad at what they do. Jarrett on Shipping Wars (which also uses uShip comes to mind....)
pilot air is a name, they don't put freight on a plane. Forward Air is decent, (again they don't put freight on a plane) only probs with using LTL freight is it needs to be put on a pallet and dropped off at their terminal.