how many outlets and fixtures can I connect to 20 amp cicuit?
The NEC requires 1 - 20A circuit for bathroom receptacles, and you can feed thru to the other non GFCI outlet, and you can connect up the lights and the exhaust fan in the bathroom if and only if the 20A circuit is specifically used in that bathroom. If the 20A circuit is used for multiple bathrooms then no you will have to find another circuit to connect your lights and exhaust fan. 

I am assuming of course that you are talking about a bathroom.