Here's something I have been meaning to do for a while....
A simple note, directly on the speedometer to remind myself to slow down.
Here's how to make one yourself.
Grab a sheet of return address labels, or similar computer-printable stickers.
In your favorite word-processing or layout software, use a template or measure your stickers to that your words actually line up on them.
Type in something clever to remind yourself to slow down.
Now print that out. If you have more than one vehicle, or want to share with friends, make a bunch at at once.
And the last step: Stick it on your speedometer!
That's right! Directly ON the speedometer, covering up the speeds you DON'T want to go! When you look down and realize you can't even see your speedometer needle, you will naturally slow down real quick!
If you wanted to make a really fancy version of this, measure your speedometer dial diameter, and draw a matching arch in some graphics software. Then you can design a sticker that perfectly matches.
For any of you REALLY advanced graphic designer/tinkerers:
Remove the dashboard from your car, scan your speedometer dial (keep the 1:1 size ratio) Photoshop it up so that it just doesn't go higher than 55 or so, print that out, paste it on the dial, and reinstall in the car. Now you have an UTTERLY STOCK speedometer that only goes to 55!
Anyways, that's a lot of work.
My version took longer to blog about it than to do it...
(LEGAL DISCLAIMER: If it is illegal in your area to have a sticker over the speedometer, don't do it. Alternatively, don't get caught. Not that Ecomodders ever get speeding tickets. Well, not for going OVER the speed limit anyways.)