Janis Whitcomb (Trotting Horse and second link) (Yahoo!, FZ10 group, 20 June 2004)...
Q : I usually get the same effect {condensation collecting on the camera lens} on entering from outside into buildings in winter time...Anyone has any idea how to avoid it?
A : A friend of mine, an Engineer for Boeing, quit his job to work as a free lance and for National Geographic. Naturally, his travels took him to different climates. He said heat was not as great a problem as cold and the only way around the condensation problem when coming in from the cold was to put the camera in a big plastic bag. The moisture would then collect on the bag and not the camera.
{Another poster, strat, suggested placing the camera under a coat if a bag was not available. However, Strat thinks a plastic bag would be better.}