If your resume is long because you have been ehm... job hopping, then it makes sense to combine a functional and chronological resume. My resume's first page is basically a functional resume, highlighting key skills. For the interested reader, plenty detail is provided in following pages. This way, I can satisfy the casual reader who wants to get a basic idea of my background, as well as the person who wants to see whether I do indeed have the specific experience (s)he is looking for.