Theres a station locater, route mapper, and overview applet on the site. They're all kind of chunky and slow (like the government), however, there is an option for downloading the Route Mapper output to a Palm PDA. I don't have a Palm, I have a laptop. So, I downloaded a "Palm OS Emulator" (typically for software development uses) from Palm. (You have to sign up for an account and all that crap, but its not hard).
Then you download the ROM from them. Get palmos35-roms-en.zip for color, then run the emulator and select this ROM from the setup window. Its a palm computer running on your screen!
You can take the route mapper output file (or ANY Palm application) and "load" it into the Palm by drag 'n' drop. Voila, the route mapper is big and clear and easier to use by far than the web version.
Now I have driving directions to LPG filling stations up and down the I-5 corridor. The route mapper also lists EV, E85, CNG, LNG, etc. as well as Biodiesel (Apparently big in the South Appalaichian region and Pacific NW.)
Anyone wondering where they would fill up with Propane should be surprised by the distribution of LPG sites on the national map.