I'm not into memorabilia but there are 3 things I fancy owning.
The original Cochrane statue from Archer's room (not a newly cast one).
The salt and pepper shakers from Archer's dining table. These went on sale on ebay a few years back but I found out too late.
The chinese dragon in Janeway's ready room.
I have a piece of the shuttle from ST:XI. It's wood
That's the only bit of memorabilia I have.
I would probably bid myself into oblivion over any of the Janeway ready room items if they came up though.