I am using the Duemilanove board and I have 2 different things that need the serial input, a GPS data stream, and a RF serial reciever to get commands from a computer. IS it possible to convert one of the other pins as a serial input?
Answer: It depends.
have a look at this
and see if it fits the bill.
This is a much less restrictive software serial.
http://arduiniana.org/libraries/newsoftserial/
Works a treat.