http://www.ecomodder.com basically a club for more 'economical' cars, hybrids etc.
I do some other minor stuff like a warm air intake to help keep the Insight in lean burn as well as block the radiator in cold weather.
Another aesthetic modification I made is to add an Mobile LED MD-550 scrolling LED sign in the rear hatch window. (The company is no longer in business.) I put up fun things like "Now Getting 85 MPG", to share with other drivers around me.
Is there a simple way to fool my ECU into reducing the amount of fuel it tells the injectors to pass? Sort of a flip of the switch 'lean burn' mode?
what TYPE of tire is the most fuel efficient?
Universal Flat wheel Covers
yay! i hit 30mpg!
ooh... and their sigs

and finally, a few tips to "HYPERMILING"
17) Avoid drive-thrus
24) Drive when it's warm out
28) Minimize idling when stopped
If you're going to be stopped for more than a few seconds, shift to neutral and shut off your engine. This is one of the main reasons hybrid vehicles get such good fuel economy in urban driving.
33) Lights on for safety; lights off for MPG
47) Drive shoeless
Some hardcore hypermilers drive in sock or bare feet so they can modulate the accelerator to the finest degree (particularly important when "driving with load" / "target MPG driving" at cruise.
70) Automatic transmission: key off, then Park
Save a few drops of fuel by modifying your shutdown procedure: when parking, turn off the key *before* shifting to Park and setting the parking brake.
105) Listen to slower music
ah... one day we'll all be like this