I have a Bryant central air systems, and have noticed that there is a constant dripping stream of water coming from the condensate line.

I can understand this during cooling in the summer, but should it be doing this during the winter?

Also - I've tried cutting back on system use, but the amount of water does not seem to decrease. How can I tell if enough water is draining out?

If it is 80% efficient it is supposed to do that. Do you have a whole house humidifier?