In general play online I never show, but I play in a weekly 'home game' (moved online for obvious reasons) and I occasionally show there...
I try not to show too much, because as mentioned it gives too much away, but occasionally it's fun, either if you hit, or it's a cheeky bluff, or just showing one card when it doesn't give away what (if anything) you had
An example of the last one and limped in with 10-2 off, the 10 hit a straight and my river bet got the other guy to fold. So I showed the 2, which hit nothing, for the lols