I find this one of the most fascinating, and insightful glimpses into the lives of fellow collectors...and the relative desirability of certain types of cards, etc.
I think I may rather resemble Mr. Ullman.
Ah, Frank, never miss an opportunity to dis one that I grew up admiring in Mr. Puckett, may he RIP....
To each his own, I certainly understand.
To answer the question, I have a card collection, in which I collect many collections of cards and other card collections (of cards)!!!
I try to organize, but it is a bit of an aberration for me, in that it is one area of my life where I am not nearly as linear in my thinking or organization as I am in the rest of my daily life and work...
There is Pre-war and Post-war
There are player Collections, spanning baseball, football and basketball
There are team collections (Cubs)
There is a family collection (which is a subset of the Player Collections, I suppose, but those branch out to all memorabilia and not just cards)
There are complete sets of teams, some minor league teams, and a few major post-war Topps
There are a few figurines (Ozzie Smith, Watler Payton, Johnny Bench)
There are a few bats (Puckett, cousins)
There are autographed balls (HOFers)
There is international baseball (vintage tobacco)
There are "Odds and Ends that Looked Cool while I was Bored on Ebay" (yes, this is the official name of the collection, and it consists of things I might not even be able to re-sell, like fairly beat-up 1960's topps stars)
There are T206 subsets based on the image background (Sunset, Stadium, and Sweaters)
And the most fascinating aspect of all this is that I own only 38 items!!!
-kidding, I have 138!