Can I point you here....
Note that the number of serial channels available differ depending on the board. Personally I play with the Mega 2560, but I've only needed the i2c port so far (a snap to use), although I'm about to play with reading my foretrex 201 across one of the 232 ports with the use of a little Maxim board.
You should find quite a few sketches to get you going though.