Well, as others already mentioned you could use instead of an IDE a separate text editor. Several come to mind;
a) VIM (or one of the family) - great editing capabilities, very customizable. Unfortunatelly, it is still an editor - not an IDE. It can be customized in a variety of ways of course, but that gets boring after a while. Also, it's syntax highlighting capabilities are somewhat wrongly made. Also has some problems/confusions with free/fixed format and f77/f90/f95 ...
b) Emacs - pretty much same advantages/shortcomings as the above.
c) SlickEdit - has very nice fortran support; unfortunatelly, modifying it is a little annoying and the support forums are not much help.
In general, editors like the above mentioned can be used, but in that case it is best to choose one from the start and stick to it; modifying your work habits as you go; since customizing everything can be time consuming to suit your needs.
Most editors have problems with fortran's syntax, since they're used to C's (where everything that "opens" has a "close").
As far as IDE's goes, your options are not that great:
a) Silverfrost's compiler used to come with it's own IDE (Plato, if I do remember correctly; it's been a while) - don't know what happened to it, and whether it still is "alive"
b) Absoft has one of it's own as well (never used it so ...)
c) There was a specialized fortran editor I once encountered; ya...something; unfortunatelly I cannot remember it's name; maybe someone else will know
d) One of the best options (which I used to use myself, so I may be biased) is Visual Studio + Resharper, which will add a few editing features to VS's editor. Most of them can also be accomplished with macros.
This post could use some editing but it is written in a hurry, so ...