I walk in the corridor, meet a colleague from the other end of the bay, and we greet each other. Sample conversation:
Colleague: Hey! What's up?
Me: XYZ project/ Meeting with ABC / Running to Building A for a meeting in 5 min!
Basically, fill in whatever you are preoccupied with then. If you are working on *classified* or *confidential* stuff, say something like "Nothing much. You?" And you know what to expect from the other guy! If you don't wanna say anything or have little time, keep on walking with a rejoinder, "Hey there! What's up with you?" Dont be surprised when the other person says "Nothing much!" or something mundane.
This kinda greeting ritual happens near the water cooler or in the elevator too...well, anywhere... The other day, a colleague and I were in the vicinity; so we decided to go for the ritual. She opened with the expected, "Hey there, what's up?" I said, "Lotsa things!" Smile. We had just added a new dimension to the ritual, and it was no more just another meaningless ritual, but a conversation starter.