This seems easily testable. Though I cannot recommend any, I'm sure there are online memory tests that let you know how you performed relative to all the other subjects. Maybe not good enough, as there is a selection bias in the sample of people who take those tests, but it will give you some info.

However, I think that you have an above average memory and are only noticing this because you usually hang around people who have above average memory as well[1]. Perhaps a more useful test would be getting your friends to take the test as well and compare the results. Maybe ask on LW for subjects? I'd participate.

[1] Assumptions:

• You have an above average IQ. I a priori assume this of all LWers.

• There is a positive correlation between IQ and memory. A quick search gives results in favor of the assumption, but I didn't dig deeper.

• You hang around people of similar IQ.