Personally, I have 7:
2 game servers, my computer that is my dedicated router/firewall (running smoothwall), my laptop and main desktop.
2 computers aren't in use yet, one is a backup webserver the other is just one to play around with.
House wide:
Dads computer
Mom's computer
Mom's Pocket PC (Brand new addition to the fleet
)
Sister A's computer
Sister B's Laptop
For a grand total of 12 computers. + enough parts laying around to build my self an other computer
( I don't get rid of computers, when I upgrade my main desktop, the old parts go to the main game server. Main game server parts go to the secondary server and so on down the line until I end up with parts but no case. I then buy a new case and thus add an other computer to my fleet).