Help! Breaker blew and half my house is dark?

Hello, a circuit that supplies my living room and rear of the house suddenly went dark. When I went to turn it back on, sparks and a huge HRRRRNG! buzz came out of the circuit breaker. Freaked me out, as you may expect. I inspected all the light switches and outlets on the circuit. One seemed bit scorched, so I replaced it. Tried to hit the circuit again, more sparks. Took the front off the electric box to look at the wires and buses, and everything looks fine. Short of calling an electrician I can't afford, any suggestions as to what I could be missing?