I’ve updated the Fortran language definition file from GNU Source-highlight to include new keywords from Fortran 90 through 2003, highlighting for numeric constants with kind parameters, and hexadecimal constants. You can find it here: fortran.lang.
I sent it to the maintainer about a month ago to have it included but my mail was returned. I’m retrying, but I’m posting it here just in case. It also may take a while to make it into packages–the latest version is 2.11 but the newest Debian package (in unstable even) is 2.4.
Update (June 13, 2009): Though I failed to mention it at the time, the above updated fortran.lang file was included in GNU Source-highlight version 2.11.1, released on December 22, 2008.