I truly wish i could say 2 or three, but sadly, it's in the 6-10 range. I routinely TRAVEL with at least 6.... My last trip to South America:
Hasselblad 203FE
Zeiss Ikon
Canon EOS3
Contax T3
Panasonic LX3
Leica R7
In addition, the stuff i left behind: Leica CM, Contax Aria, Nikon F80. And, i should have had a Canon dSLR, but i sold my 5D too early and haven't taken delivery of the MkII.
But, i will, eventually, sell a couple of the film SLRs. And, maybe the Ikon at some point. I'd like to have it down to the Hassy, 5D2, the Fuji GA645i i just acquired, and a T3. Sheesh. Even that sounds like too much.... I really admire (but don't understand) people who shoot with one camera for years. But, in a way, i must think it's the sign of limited interests. You sorta have to restrict yourself to one kind of photography. I guess it's easier if you're a 'street' shooter. I'm certainly not like those guys on dpreview, who have a lens to cover every possible focal length, from fisheye, to 600mm. I need only 24 to 100mm or so. And, anything outside of 35 to 85 is a rarely used luxury. I, essentially, shoot people: fashion/portraits/nudes, and some 'travel.' One would think i could do that with two cameras, right?