Since a few of you have asked, here is mine:
I got rid of the closet organizer and installed two shelves in the closet, plus some fluorescent lighting. This will be my main workspace (if I ever finish getting organized). The lower shelf is at the height of my elbow, so I would stand while building.
In hindsight, the upper shelf comes out a bit too much as I can bump my head if I'm not careful, but the deeper shelf allows me to put more stuff up there. I have stored sets/boxes upright to make use of the vertical space.

Just some big/tall shelves to hold sets:

Towers of drawers to hold larger pieces (right-most one is all old-light grey bricks!):

In my rec room in the basement, I have a 40"x50" board mounted on the wall that I will cover with 32x32 baseplates so that my kids (currently 5.75 and -2 months) can build on, studs out. Unfortunately, the board is more like 39.5 x 49.5, so I haven't applied the baseplates to it yet because they will hang over just a bit. For those of you that work with wood (Brickhead, I'm looking at you), any ideas on how I can add on that extra bit of width?
Unfortunately I still have a ton of sets stored in a spare bedroom at my parents' house. Between 2003-2008 I collected a lot of themes (Castle, Wild West, Trains, etc.), including retired sets. In addition to those, I also parted out sets for the purpose of building MOCs.
There's no way I can fit everything into my new house so going forward, I need to be extremely selective on what I buy (but Modulars are a must!). It also means that over the next few months/years, I will need to sell off most of the sets I've collected over the years...