Usually, four.

Victorinox Classic (for open letters, boxes, trimming fingernails, etc)
Victorinox Money Clip (to hold cash)
Gerber Air Frame (this one doesn't get used for "normal" duties)
Leatherman Wave (the original one, as a portable tool kit)

and depending on the environment I'm going into, I may also add a Benchmade 100RR or another small fixed blade from my collection.

Going out back, I usually add a Gransfors Mini Belt Hatchet, and my Benchmade 190 and 192 hunting knives, but I have others to choose from.

Three. All of them in cordura belt pouches, hidden from the PHRASECENSOREDPOSTERSHOULDKNOWBETTER., under untucked shirt.
1. Victorinox Blackchamp
2. Gerber Urban Legend 700
3. Benchmade Mini-Griptilian 555

Four
Leatherman supertool in a belt sheath
Kershaw Leek right front pocket
Cold Steel Tuff Lite attached to a Streamlight Key Mate left front pocket
Cold Steel Voyager X2 in waist band

Where I am and who I'm with dictates which one I use as much as the task at hand.

Leatherman Wave (old version) on belt.
Kershaw Blur in left front pocket or clipped to belt.
Countycomm single edge mini razor on survival keychain right front pocket.