What place do you find yourself drawn to? Do you have a house in one of the cities? Maybe you've taken over an abandoned fort to stockpile all your loot.
Personally I keep using Breezehome in Whiterun, even though I have a house in all the other cities. It has most of my junk stashed away in it, just a pitty there are only 2 bookshelves in it.
What about you?