PySerial
PySerial is a library which provides support for serial connections ("RS-232") over a variety of different devices: old-style serial ports, Bluetooth dongles, infra-red ports, and so on. It also supports remote serial ports via RFC 2217 (since V2.5).
Projects using PySerial
BitPim - crossplatform application to view and manipulate data on CDMA phones from LG, Samsung, Sanyo and other manufacturers.
RFIDIOt - an open source python library for exploring RFID devices (see also "RFID enabled e-passport skimming proof of concept code released (RFIDIOt)" and "Code highlights e-passport eavesdropping risk")
t616hack - a distribution providing access to the contacts, phonebook and messages on the Sony Ericsson T610/T616 and compatible mobile telephones
jaraco.nxt - a package implementing low-level API communication with the LEGO Mindstorms NXT robot kit.
Twisted - Uses pySerial to provide an asynchronous serial port transport which can be used like any other stream-oriented transport (eg TCP, SSL).
Alternatives
Bluetooth connections can also be handled using the socket module, provided that support for Bluetooth is present in the underlying operating system and has been compiled into the Python distribution being used.