Hi Fred, welcome to the site.
I'm sure you will have many envious comments from the Honda crowd about your HF.
As for mods, dive into the Ecomodding Central and Aerodynamics forums and you'll find more ideas than you can shake a wrench at.
I'm sure you've already seen the driving tips:
100+ hypermiling / ecodriving tips to increase gas mileage - EcoModder.com - that's the fastest/cheapest way to significant MPG improvements.