hi there,
i don't know wich distro you use but g77 will do the trick.
if you need fortran 90 is not so easy, AFAIK there is an INTEL compiler free but you must register and blahblahblah..
if you have mandrake installed try that at the terminal prompt..
Code:
g77 your_program.f -o executable
and now you have the simplest way to compile a program.
regards
slackie1000