Just a note for anyone else trying to do this: building a development environment for a Hitachi's (nee Renesas) H8/500 platform these days can be moderately difficult. You'll need binutils 2.16.1, which is the last release to support H8/500 as a target. Build with ./configure --target=h8500-hms --prefix=/x/y/z (where /x/y/z is the location you want to install to), and it should go smoothly (at least, it did so on Fedora 13 x86_64, using gcc 4.4.4; I'd seen other reports that an older version was needed).
Sadly, GCC is proving to be a dead-end for me. No released versions of GCC that I can find ever shipped with support for H8/500 (although one report suggests that a development build of 2.96/pre-3.0 ended up working, although I think he's referring to the GNUPro-96q3 release), although I've found several suggestions that Cygnus' GNUPro shipped with support for it, at least once upon a time. If anyone has chased this particular item down, I'd love to hear it.
(Why would anyone care about a dead embedded platform? It's the CPU used in late DSM ECUs: 98-99 Eclipses, in particular.)