We all have our own arsenal of poker plays and moves. Some you use frequently, some you dont. Showing cards, at the right time, with the right players at the right table can be very useful.
I would say, use your judgement of the situation, if you think showing a bluff or a strong hand will benefit you in some way at some point later in the game, then do it. There are no 'never do this, or never do that' in poker. Its all situational.
As LeanAndMean added, telling someone you had a certain hand can also benefit you. But also remember, showing can sometimes work against you as well.