"hstags" is a relatively sophisticated program to produce Emacs TAGS
files for Glasgow-Haskell-compilable programs.  (It is "sophisticated"
only in that it uses the GHC parser to find "interesting" things in
the source files.)

With GHC 2.01: doesn't work yet.

A simpler alternative is Denis Howe's "fptags" script, which is
distributed in the ghc/CONTRIB directory.