The Degrafa graphics framework for Flex is very slick. I have been using it on my flex real-time monitoring applications. Here is a configurable meter that I created using Degrafa. Feel free to use it if you find it useful.
Flex Degrafa Meter
Have some new updates to MpgGenie.com. You can now view an Adobe Flex application that dynamically shows commuting costs on the individual vehicle pages. Here is the page for the Toyota Prius Hybrid-Electric car.