http://en.wikipedia.org/wiki/One_wire
The 1 wire interface can be implemented through the serial port with a dongle based on the DS2480B from Maxim. If you use this dongle, you need to use the serial interface instead of 1 Wire.
Another way to interface to 1 Wire is to use a simpler dongle with the serial port.
An application note from Atmel suggests using an UART for implementing the bit transfers. The driver schematic provided are for interfacing to the TTL levels of an UART.
(See AVR318: Dallas 1-Wire master)
Based on this application note, I have made a dongle using 2 common transistors and a couple resistors. This dongle uses the normal RS232 levels of the serial port and convert them to the 1-wire levels. It can also be used with common USB to serial converters. See schematic below.
My setup consist of the dongle with 2 transistors, connected to a serial port. On the 1 Wire bus, there is a DS2450 connected.
There are several adapters for 1 Wire; one of them is made with several diodes and is connected to the serial port. However, I suspect this circuit may cause some problems because of the ground reference.
http://owfs.sourceforge.net/adapters.html