Human blood groups are of 4 types with negative and positive of each types (Wikipedia). But according to this forum thread there are some other types too:
I'm going to make software for blood donation, where I need to put a dropdown list of actual blood types. I had intended to use:
[ Select Blood Group V ] [ O Negative ] [ O Positive ] [ A Negative ] [ A Positive ] [ B Negative ] [ B Positive ] [ AB Negative ] [ AB Positive ]
But now I am uncertain whether this is appropriate. What is the most suitable list of blood types for donors?
As far as I am aware it is the RhD and ABO blood groups that matter with blood donation - though you may wish to contact a blood donation organisation for more specific information on how they handle & categorise the blood.
But using just RhD and ABO gives 8 combinations, positive and negative of A, B, AB, and O. You can find out more about the blood groups, blood donation, and the characteristics of blood groups here.
The subgroups you allude to are due to differences in the number of the antigens on the surface of the blood cell, for example the A1 group have ~1,000,000 A antigens per cell whereas A2 variants have ~250,000. The A group has ~20 subgroups, the vast majority of people are A1 (~80%) or A2 (~20%), and the other groups make up less than 1% of the population.
These two subgroups are interchangeable as far as transfusion is concerned, but complications can sometimes arise in rare cases when typing the blood.
If the blood donor is filling out the info, I recommend you have one dropdown that offers: A, B, O, AB, don't know… And a second dropdown that offers Rh +, Rh -, don't know. And be aware that the average person is not likely to correctly know their blood type.
Actual laboratory blood typing checks for a large number of possible differences between blood cells beyond just ABO types. The clinician or technician will not use anything as simple as either your drop-down OR the slightly more complex drop-down in the referenced forum post.
If you still want to know more about "what the actual blood types are," recognize that there are LOTS of blood types, including the MNS system, the Kell system, and the Lewis system: http://en.wikipedia.org/wiki/Blood_typing