Weird puff of smoke

[sbmike]

A few days ago when I started my '04 truck (22k miles on it), I happened to look in the rear view mirror and saw a small cloud of white smoke apparently coming from the exhaust pipe. It was the first time I had started it in a couple of days and it was early morning but not too cold outside. I've never had that happen before and it has not happened since. Any of you mechanic-types have any idea what the cause might be? Oil pressure is ok and oil level is good too. And, no, I had not eaten beans, boiled eggs and drank beer the night before. ;o)