The 1-Wire family is a lot more than some great temperature sensors. (There's an enthusiastic discussion on using 1-Wire temperature sensors over at the Software Interfacing forum....http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1161557194
EVERY 1-Wire chip has a unique ID embedded, so you can use 1-Wire devices for access control, like the RFID devices that other Arduino threads are exploreing. (With 1-Wire ID, you have to make physical contact with a reader... but the RFIDs we're working with require near contact, anyway.) The iButton range consists of 1-Wire chips embedded in cannisters like button cells. You may have seen employees at pubs, etc, authenticating themselves to the cash register with these devices.)
For the Arduino community, the 1-Wire counter chip, DS2423, would seem to be an asset. It continually monitors two inputs, and counts the edges on them, separately. Whenever the master (the Arduino) chooses to go to the chip and ask, the chip reports the count to date. Great for wind speed monitoring, etc, etc, etc.
There are at least two barometers built for the 1-Wire system. The master (the Arduino) just asks the 1-Wire chip for the current pressure in almost the same way as the work done on the Arduino to date fetches temperatures from the DS18x20 chips.
Much (too much?) more at..... http://www.arunet.co.uk/tkboyd/e1didx.htm
You can see a weather station which collects all it's data across a MicroLan (trademarked term for a network of 1-Wire chips) at... http://mon277rr.dyndns.org/
(For the full story of the weather station, see.... http://sheepdogsoftware.co.uk/ssds043.htm
(Pictures of iButton access control equipment at... http://wolfvansecurity.com/product/ibutton.htm