Alan Aragon's first blog posts were on this topic:
From what I hear, Australia seems to have good accreditation. I haven't heard of anything worthwhile anywhere else. I have a CSCS, but I'd probably equate that to having a 2-year college (Junior College/Community College) degree.
The IOC seems to have a pretty good Sports Nutrition accreditation program, but it's expensive and takes 2 years to complete:
If you can't find anything satisfactory, you could always do your own independent reading/learning.