The Royal Photographic Society have these qualifications, the bottom level of which is the Licentiateship, known as the LRPS. There are basically two ways you can achieve this. As it says on the RPS's web site:
The Licentiateship is awarded either for competence in practical photography, or by passing of an appropriate examination in photography recognised by The Society.
Basically you need a set of 10 photos. The tricky thing is, the photos have to work well as a set in addition to being good photos in their own right, so you don't necessarily just choose your 10 best shots, some judicious mixing and matching is required.
I am vaguely putting together a set, though when I have something approaching a set, I will need to see about going along to one of their Distinctions Advisory Days or Workshops to get some feedback.
[Edited to remove link to a Flickr set that I hadn't realised was friends/contacts only. Apologies to anyone who might have tried to view it.]
Examples of the kind of thing that is required are available if you ferret around on the RPS web site. You can also download an interactive thingy that allows you to pick photos from a bunch and arrange them into what you think is the best possible set.
One reason I was so pleased with the shots I took yesterday was that I set out deliberately to capture something not unlike what I achieved. The same goes for the shot of the barn. Previously when I've taken good photos, it's been largely a matter of chance and grabbing the moment, which is a useful skill, but it's also nice to be able to plan a shot and then get what I intended.