Is your Jeep lifted with bigger tires? Losing the lift and returning to stock tires will give you back some of your mpgs.
Otherwise, some of the tuners offer "economy" tuning options. I understand the overall experience with those tunes however is to drain power, so if you were hoping for power plus better mpg's those aren't going to help too much.
There's just not much that can be done mechanically, which is why better driving habits, returning to stock tires, and a tuner is about all most folks can do.
Unless of course you wanted to install a supercharger, which should net better gas mileage and a substantial increase in power.
**Edit: Oh, and the throttle body spacers are snake oil. I've heard mixed reviews on the intakes/exhausts, but I've never heard anybody proclaim the benefits of TBSs. At most, folks are neutral to them--i.e., "I installed it and noticed nothing."