The 6.6 gallon bookshelf (currently housing mystery snail eggs waiting to hatch) is on...well...a bookshelf right behind my desk. It is about to be joined by a second bookshelf tank this weekend.
The Buddha tank is my PFR tank. (If you look close you can see one on his head!) This one is a 10 gallon and is on the end of my bar.
The 5 gallon hex houses one of my betta's (Grover). It is on a built-in unit in the family room.
The jungle QT tank, currently housing my other betta (Apollo) is a 10 gallon on a stand next to my desk.
(My office actually has tanks on all 4 walls: the bookshelf behind me, the QT on the wall to my left, a 29 gallon on the wall to my right and a 55 gallon on the wall opposite my desk. I LOVE my office!)