This module encapsulates the access for the serial port. It provides backends for Python running on Windows, OSX, Linux, BSD (possibly any POSIX compliant system) and IronPython. The module named "serial" automatically selects the appropriate backend.
The first of several wiki pages at elinux.org which comprise a hardware compatibility list for the Raspberry Pi. You might want to have this page loaded on your phone or tablet when you go shopping for new peripherals.